system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do video games tend to require a loading screen when you walk into a building? I’m thinking about games like Skyrim which let you roam their huge open world without any loading but require a load screen to enter a small building.
gpt
A couple possibilities come into mind. First, towns tend to be a lot more dense. That is, there's a bunch of stuff in a relatively small space. If all the interiors of all the buildings had to be rendered when you enter the city, it may exceed the ability of many systems to render well. So to mitigate this, the game waits until the player enters a building before rendering it.

Another possible reason is simply to allow more modular programming. The interior of the building doesn't have to exactly match the outside dimensions, allowing the developers a little more room to make elaborate interiors without worrying that they might infringe on the constraints imposed by the exterior. So you can have one map designer working on the overall layout of the town while another works on the interiors without worrying about potential conflict.