it's definitely a matter of culture (just look at cartoons, they're not proportional for shit and tend to avoid even reminding you that perspective exists), but also i think it's a factor of who is drawing things.
If you're a monk drawing stuff all day you're probably not going to bother with anything you don't have to, or that doesn't entertain you.

Well, the Egyptians had the same art style pretty much unchanged for thousands of years. Archaeologists believe that their proportions were based on mathematics, and was probably taught as the only way to make art.
Many cultures have prioritized stylized art over realism.