Everybody Is Single

Despite the number of experienced, professional people at the firm/lab/force/whatever, everybody on the staff is single. Some may have once been married, but they are now divorced. It might be mentioned that the hard hours their profession demands cuts out the chance for the standard nuclear family, or they may simply be Married to the Job. Usefully, especially in sitcoms, any attractive guy/girl they meet and try to hit on will also be single, unless them being taken is relevant to the plot.

In reality, though, the writers just want as many people to have as many potential love/lust interests as possible.

This is common in Sit Coms such as Friends, but is more jarring and noticeable in dramas such as ER and CSI. Actors portraying these perpetually single characters are often married themselves, showing how odd the trope is for people of their age.

Compare All Love Is Unrequited.

Anime and Manga

 * Played largely straight in the original Mobile Suit Gundam, which isn't surprising, since most of the main cast are junior officers still in their late teens. Averted in Zeta Gundam, with two couples from the original who had gotten married in the intervening years. Most Gundam shows play it straight, though.
 * Narrowly averted in Patlabor, as shinshi often mentions having a wife at home. The rest of the main cast are single, but considering their personalities, that's hardly surprising.
 * In fact, most Humongous Mecha shows usually play this straight with the pilots and support crew, with a few exceptions, probably the best example of which would be Godannar, where the pilots of the titular robot are a husband and wife.
 * Double subverted in Fresh Pretty Cure!. It seemed that, finally, in the sixth season of the Media Franchise, a character would be introduced who was already taken... but the "boyfriend" turned out to be her brother.
 * Fullmetal Alchemist: the only married couples are Maes and Gracia Hughes, Izumi and Sig Curtis and King Bradley and his wife, . Especially notable given that the series is populated with Good-Looking Privates.
 * Funny thing about Magical Girl Lyrical Nanoha, despite the fact that a decent part of the cast are parents, the only characters who are currently married are Chrono and Amy. Other parents either adopted their kids while single or lost their mate before the series began.
 * Averted in Umineko no Naku Koro ni - everyone in the Ushiromiya family, with Battler and possibly Rosa as an exception is either married or in relationship.
 * Ouran High School Host Club's cast is made up mostly of singles. All the Host Club members and their customers are single (as far as we know), as is Haruhi's father (widower), Tamaki's father (divorced, and forcibly separated from his lover and mistress), Tamaki's grandmother (widow), and Ranka's co-worker and friend Misuzu (divorced). The only couples in the series are the Hitachiin's parents, Kyouya's parents, Kyouya's sister and her husband, and a few students at the school who are in perfectly arranged marriages.
 * Ouran High School Host Club's cast is made up mostly of singles. All the Host Club members and their customers are single (as far as we know), as is Haruhi's father (widower), Tamaki's father (divorced, and forcibly separated from his lover and mistress), Tamaki's grandmother (widow), and Ranka's co-worker and friend Misuzu (divorced). The only couples in the series are the Hitachiin's parents, Kyouya's parents, Kyouya's sister and her husband, and a few students at the school who are in perfectly arranged marriages.

Comic Books

 * Any superhero comic book character. Expect any long-term relationship with other superheroes to fall victim to No Going Steady and for non-superpowered spouses to end up Stuffed Into the Fridge.
 * Notably averted by Spiderman. He managed to hang onto Mary Jane for decades. At least until the relationship was RetConned out of existence in the One More Day storyline. That, and Lois and Clark.
 * Averted in the DCU by the Golden Age Flash, Jay Garrick and his wife Joan.
 * The second Flash was in a stable relationship as well.
 * Invincible and Atom Eve are a good example or an aversion.
 * Averted by Reed and Sue Richards, aka Mr. Fantastic and Invisible Woman in Fantastic Four.
 * Most of the faculty in Archie comics, with the exception of Coach Clayton. And he's possibly the only subversion because his kid attends the school and is friends with Archie.
 * Seems to have creeped up on The DCU with The New 52. Barry Allen is no longer in any kind of relationship with Iris West (effectively wiping out Wally West in the process), Superman is no longer married to or interested in Lois Lane...

Film
"Millie: [flirtatiously] Hi, I'm Millie. Player: [brusquely] Hi. I'm married."
 * Though this happens in a lot of sports movies, it's extra-noticeable in The Game Plan starring Dwayne Johnson. Not only is almost the entire team of professional sports stars unmarried and single, all but one (besides Johnson's character) aren't parents either, and are merciless with their teasing about his new status. In real life, of course, a lot of professional sports stars are married and/or parents.
 * Averted explicitly in at least one instance in the baseball film Bull Durham: when Millie, the younger baseball groupie (and protege to Annie Savoy (Susan Sarandon)) is working her way down the bench introducing herself to various Durham Bulls players, she flirts with one:


 * Possibly averted again, when.

Literature

 * In the Doctor Who New Adventures novels, the decision to give ex-companion Bernice Summerfield her own spin-off series—in which, as lead character, she would be expected to participate in romantic-interest subplots—led directly to the messy collapse of her marriage, which upstaged the violent deaths of a tenth of the Earth's population. This, less than a year after an entire novel was devoted to the wedding and much effort was expended in assuring readers that it was Happily Ever After-type True Love.
 * Exception: Jasper Fforde married off the character of Thursday Next in her first book, specifically to avoid romantic subplots in the rest of the series, and get on with the main story.
 * Subverted in The Moon is a Harsh Mistress, in which the protagonist is married... but still eligible for a love interest subplot, as it's a group marriage. (In fact, two spouses, one of each sex, get added to the marriage over the course of the book. The new wife is the protagonist's new love interest (and all the other spouses grow to love her too), the new husband is a friend protagonist and love interest acquire during the plot, who thoroughly charms all the other spouses.)
 * A pop literature aversion: in the In Death series by JD Robb, Fair Cop Eve Dallas gets married shortly into the series, and has stayed that way throughout the rest of the books. Her best friend is married and has a kid, and her aide is living with a serious boyfriend. Many of the other supporting characters are also shown as more or less happily married, with a few exceptions.
 * In Harry Potter, none of the staff at Hogwarts seem to be married or indeed to ever have been able to sustain a proper relationship. The only counterexample is in the future, with
 * JKR stated in an interview that some of the teachers are married, though. Can't recall if she mentioned how their living arrangements work...
 * Pottermore reveals Professor McGonagall was briefly married. They lived in Hogsmeade, so McGonagall would have an easy commute to Hogwarts every day.
 * Bellatrix Lestrange is a weird aversion. She's married, but her husband is rarely mentioned in the books and never mentioned in the films.
 * The Honor Harrington series has this in the earlier stories as a common issue. While there are many couples, the main character is very single with romance subplots. Loads and Loads of Characters with the Author taking 12 books to start cleaning up loose ends.
 * All 7 Friends of Narnia in The Last Battle are single. None of them married either in Narnia or England.
 * Subverted and played straight in The Dresden Files. Michael's status as a happily married, loving father is a major plot point in some of the novels, but Harry and Murphy's near-perpetual single status is much important to the series dynamic. Both of them have had a Love Interest or two, but these tend to either not be very serious or end rather...explosively.

Live-Action TV

 * Any show with military underpinnings usually does this as well, since it would be "improper" to actually have a relationship within the ranks. Star Trek in particular usually plays fast and hard with this trope (and when two officers do get married, they always seem to be the same rank at least).
 * Averted and played straight in Women's Murder Club; one of the main characters is a single workaholic whose obsession with her job destroyed her marriage, but another is happily married with kids and a third is in a long-term relationship (although she's a commitment-phobic with a tendency to stray).
 * On 24, this is universally true at CTU—however, this is partly because of 24's recurring theme of the conflict between family vs. duty. Hence, there are a lot of divorcees and widows featured on Twenty Four.
 * In season 8, this was averted by Cole and Dana
 * At the beginning of the Battlestar Galactica miniseries, almost every member of the main and supporting cast is single, but by the end of Season 2 everyone is already hooked up or on their way there. During the year-long gap in the timeline between the Season 2 finale and the beginning Season 3, the Love Dodecahedron of the previous season has resolved itself into four reasonably Happily Married couples.
 * The only married character of Criminal Minds divorced in the third season--but everyone's favorite tech kitten is dating Buffy the Vampire Slayer's Xander, and it looks like certain other characters might start getting some... Also, JJ has been living with and dating Will since season three. They even have a son together!
 * Grey's Anatomy begins with all of the young employees of Seattle Grace at least nominally single.
 * The Chief and Bailey were both stressfully married, McDreamy had just split with Redheaded Doctor after banging McSteamy, so the grown-ups weren't even coping. In fact given the state of Izzie-Alex, George-Callie and Yang-Burke GA is not really an advert for the medical profession.
 * In later seasons we get more stable relationships. Meredith and Darek are happily married and Owen and Christina are giving marriage a fair shot. Alex and Izzie got married but that ended badly when Izzie was written out. Even Mark seems to be looking for a stable relationship. Arizona has proposed to Callie even with the entire Callie-carrying-Mark's-baby debacle.
 * All of the doctors in House, M.D. (with the exception of Wilson, who eventually gets a divorce from his third wife during the run of the show) are single. A patient does a Lampshade Hanging by saying this is why he's not interested in a medical career.
 * Taub, Cameron, Chase, Foreman and Thirteen are all doctors and none of them are single. This only leaves Cuddy, House and Wilson single in the primary cast. Kutner doesn't count.
 * And then everyone breaks up except for Taub and his wife (until they divorce later in the series). On the other hand, Cuddy gets a boyfriend breaks up with him. Then she dates House for a while and then broke up with him.
 * Going strong so far on The Mentalist. Viewers know little of Lisbon and Cho's personal lives (except Cho's seems to consist largely of working steadily through very thick books), with the impression they're too consumed with their work to bother. Rigsby loves van Pelt, but van Pelt runs like a frightened rabbit from the idea because as the junior member of the team, she'd get transferred out if she started dating a coworker (and she doesn't come off as that into Rigsby anyway). Jane, meanwhile, lost his wife and daughter to a pissed off serial killer he was helping to hunt, and still hasn't recovered emotionally.
 * Cho was revealed to have a girlfriend and . The impression of consumption with work, however, remains strong, and social lives outside of work seem virtually nonexistent.
 * None of the main cast of NCIS are married, and Gibbs, who has had three divorces, is rather cynical on the subject of marriage.
 * This could be a Double Subversion. McGee and Abby dated at one point, and Tony's supposedly a ladies' man, but never gets serious with anyone. And then it gets averted outright with Vance.
 * All versions are represented in New Tricks; the boss is a single workaholic, one of the detectives is a multiple-divorcee and another is a widower. Ironically, however, the most psychologically-screwed up of them all is also the only one who is happily married, and has been for a good long time.
 * Everyone in the mayor's office in Spin City is single, except for the mayor himself, and he gets divorced during the series. Paul does attain a happy marriage at one point, but his wife later leaves him to become a nun.
 * On The West Wing, the president and vice-president are the only people in the entire administration who can hang on to a spouse. The show suggests that this is one of the sacrifices you make by working for the President. Leo McGarry's marriage falls apart because of the demands of his position as White House Chief of Staff, Sam leaves his fiancee to work for the Bartlet campaign, CJ fails to get it on with at least four men during the show and Leo's lawyer girlfriend vanishes during season four.
 * Averted somewhat in the final season when
 * Santos is also notoriously happily married with his wife often delaying him for a hook-up.
 * This is true of all of Sorkin's movies and TV shows; he just can't write couples very well.
 * The central characters in Las Vegas, except for Ed Deline, mostly stay out of serious relationships. Samantha is Allergic to Love (although we later learn that she was married), Mary wants to settle down but can't make it last, Mike and Danny date multiple girls, and Delinda flits from man to man until she and Danny get together near the end. In season 5, new owner A.J. Cooper had a wife that he never talks about.
 * This was the premise of Sex and the City for the first several seasons. Near the end, though, they all wind up either married (Miranda and Charlotte) or in serious relationships (Samantha and Carrie).
 * All of the main cast of Cold Case are single, widowed, or divorced.
 * As mentioned in the summary, CSI is this to a ridiculous extent. Subverted with Grissom and Sara, who are married, but since neither one is a regular character anymore, we're right back where we started. (There have been rumblings about Wendy/Hodges and Catherine/Vartann, but neither are canon as of yet.)
 * Warrick got married which surprised all the other characters since they did not even know that he was seeing anyone. The marriage is rarely mentioned on the show with the implication that Warrick is trying very hard to keep his professional life separate from his private one. When he gets divorced it comes equally out of the blue and then . The audience does not really get to see the wife.
 * Subverted in the first episode of the British sitcom The IT Crowd in a blatant parody (Jen even says it's just like Ally McBeal): "That's the sort of place this is, Jen. Lots of sexy people not doing much work and having affairs." Of course, Moss and Roy are both single because they're extremely nerdy.
 * Only Gwen in Torchwood has a partner, Rhys. Captain Jack encourages her to stay with him and not let her work consume her... it doesn't go well.
 * Although Ianto and Jack later officially became a couple, so it's was subverted in series 3 when all of the Torchwood team were in a relationship at the same time.
 * In series 4, Miracle Day, the new Torchwood team and the Dark Messiah hired by PhiCorp are single as well.
 * On the American version of The Office, every character with the exception of David Wallace has at some point been single. All the ones with kids are divorced and while a few have been married or are in relationships, none have been for the entire run of the series.
 * Firefly averts this trope somewhat with Zoe and Wash. Joss Whedon, who liked the idea of a happily married couple, had to fight a bit for this with the network. (All the other characters are single at first, but then, they're a couple of renegade thieves, a wandering minister, a prostitute and a mentally-unbalanced teenager, so what do you expect?)
 * Occurs in Stargate SG-1 even though Sam and Jack clearly have feelings for each other (and do eventually admit to them) due to their ranks and roles. Various SG team members start dating at different points throughout the series, but nothing serious ever comes of it. Daniel is initially married, but since his wife gets possessed by the Goa'uld in the first episode, he might as well be single. This trope is lampshaded when everyone expresses extreme surprise that Teal'c has a wife and son, but that's mostly because earlier he told them he hadn't left anyone important behind when he defected.
 * The show's USAF technical advisers put the kibosh on a proposed Sam-Jack relationship that the writers had been planning.
 * there is the Daniel/Vala pairing, and it sorta did happen, but then didn't since there was time travel
 * Carter and Pete Shanahan as well as Lantoosh the Tok'ra
 * Almost averted in The X-Files, Scully was originally supposed to have a boyfriend named Ethan. A scene with him in the pilot was filmed but cut when the idea was scrapped before the show premiered. Mulder and Scully instead remained single until finally hooking up with each other sometime in the later seasons. Skinner is shown to be married but we only find out about this in the episode where he gets divorced.
 * Initially true in Bones, but notably averted by the eventual marriage of the on-again/off-again.
 * Though they all date throughout the show.
 * When Parks and Recreation started, Tom was the only character who was married. He later got a divorce (in an episode titled "Tom's Divorce", no less).
 * 30 Rock has two aversions in its main cast. Tracy Jordan and Pete Hornberger have been married for the entire run of the show.
 * 30 Rock has two aversions in its main cast. Tracy Jordan and Pete Hornberger have been married for the entire run of the show.

Professional Wrestling

 * Used constantly in Professional Wrestling, except in cases where a spouse and/or children would add drama to the angle.
 * Averted a little with HHH and Stephanie McMahon, as their marriage is frequently used in feuds.
 * There are the two classic examples of Macho Man Randy Savage being married to Miss Elizabeth for years before an on-screen wedding, then still using her as a valet for years after their divorce, and Kevin Sullivan pairing his wife up with Chris Benoit and booking his own divorce.

Video Games

 * Phoenix Wright: Ace Attorney. Throughout the series, only 3 of the clients, and none of the victims or main characters, are married/have married parents (possible exception for flashbacks to Nick and Edgy as a kid, even though his parents aren't mentioned). Some (like Ms. von Karma) are never even mentioned, the Feys (Mia, Maya, Pearl, and are specifically said to come from unstable families, and Trucy's mother is missing from an accident. But none of the main characters (possibly excluding Manfred) have ever been married.
 * Manfred seems to subvert this even further, in that he mentions having a granddaughter. Neither Edgeworth or Franziska are ever mentioned to have children, and it's very unlikely so he's probably got another (perfect) kid.
 * Ship teasing is probably the main reason here. There's pretty strong hints for Phoenix wanting to be with multiple different characters.

Real Life

 * Not actually considered much of an issue in the British Army, provided those involved are not in the same chain of command, i.e. no boinking the boss.
 * The US military rules about "fraternization" are thus: 1) The two parties cannot be in the same chain of command. 2) You cannot cross the officer/enlisted divide. 3) You'd both better be either married to each other, or not married to anybody.
 * Note that #2 can have exceptions, as long as numbers 1 and 3 are followed. See #3, bold item 2, here.