Because movies have gotten so much better over the last HUNDRED YEARS and everything is always created by people who grew up with movies so the director/producer/writer etc are all passionate fans and there's no such thing as corporate decision-making influencing creation to attract the widest number of viewers or appeal to the lowest common denominator.
We're kind of screwed aren't we? I don't really see mainstream gaming getting better ever. I guess the consolation prize is this isn't just endemic to the game's industry; the bad news is it's endemic to EVERYTHING in our culture. TV, movies, book, games, publication, food, all of it is just full of "professionals" who know how to squeeze every single drop of blood from a product. That's why it's called mainstream, it's what the people with money are making; and the people with money know how to keep making money, that's why they're there in the first place.