It's reflective of a culture of cynicism. The hero cannot win without compromising his/her own morality and so must chose to sacrifice it to defeat the antagoni

It's reflective of a culture of cynicism. The hero cannot win without compromising his/her own morality and so must chose to sacrifice it to defeat the antagonist. The is perceived to be more "modern" and "realistic" way of story-telling. See Man of Steel as one of the prime examples of a cynical culture destroying one of our most optimistic characters.