A big part for a lot of movies is that they're able to translate well to overseas so a lot of it doesn't get very complicated so it works for all international markets. the thing is i don't even know if i fully believe that concept, it's not like other countries can't have in depth and rich stories, but i'd reckon it is just so much easier to transfer it that it isn't seen as economical to have to slightly rewrite shit to make sense to certain audiences. A lot of people listed other good reasoning here too