Mainliners in film

This year's Sundance festival featured several films offering unflattering portrayals of evangelical Christianity. Alison Willmore raises a good question about independent cinema:

If faith is still such an important part of American life, why is it met with such a lack of empathy in so many indies that theoretically go in search of a more sincere, less "Hollywood" version of characters and stories?

Part of the problem is that, like Chekhov's gun, a character's faith isn't generally introduced in a film unless it's going to have something to do with the eventual outcome. If religion is just a normalized aspect of someone's life that he or she is not going to have challenged, including it on screen could be seen as a loose end. But that means that when you see films with themes of contemporary religion, they're either there to fill in preexisting and frequently negative assumptions, or religion is what the film is explicitly about.