The average movie length is 110 minutes, and you just can't get that much done in that time. It takes history and careful detail to reveal character. Public speakers know that very few text pages go into an single hour's lecture. You certainly can't finish a book in that time. That's why most books do poorly as movies.
Movies have to leave out too much emotional history.
Movies want to ascend to the level of an epic novel, but that's cheating the movie. It's not designed for that sort of feat, and it shouldn't try. Movie length fits much better with short stories. So most literary short stories rarely make acceptable movie material. Perhaps all these constraints just show us that movie-making can never be a fine art.