The Law of Conservation of Detail/Analysis
The law can be applied to video games as well. If any detail of the game requires a significant investment of time to develop, it will be a primary detail. One-off NPCs rarely ever get anything more than a generic sprite/character model, have only the most basic walking animations, and have no name. You can tell that a character will play some role in the plot if they have an unusually complex character model or a headshot next to their dialog (unless plenty of other characters have that same headshot). Plotwise, this serves to separate Round and Flat Characters.
Since artists create video game worlds from scratch, scenery also obeys the law. Say they set a level in a supermarket; a real one stocks thousands of products. In the time it would take to design all that non trademark-infringing packaging they could make several entire games. So they use a handful of designs over and over. Fortunately the trope works to their favor: we accept less detail because it is not central to the game.