The Supergirl show achieved that largely by instead choosing to undermine Superman, that isn't exactly a great improvement. *cough* Though it should have been unnecessary, as it should be here for a Batgirl show.
I blame, in part, writers and directors who are unable to conceptualize the idea of the Hero *not* being the most important person in the world of the story. Its not enough that you are the hero of *this* story, that *you* have to deal with this problem; if someone else somewhere exists who is doing something else big and important, it somehow diminishes them. The only worthwhile story is one where the whole world revolves around it and you. Maybe moviemakers have been consistently taught the idea that nothing exists offstage and offscreen, and so are poorly suited for adjusting when people start realizing "Um, no, that is BS".