Here's a theory I have:
Superman's parents told him maybe he shouldn't have saved that school bus full of children, and that he doesn't owe this world a thing.
Batman brands criminals, knowing the brand will make them targets for murder in prison.
Wonder Woman abandoned the world for a century after she saw the atrocities of the first world war.
We haven't been watching the three founding members of the Justice League. We've been watching the three founding members of the Justice Lords.
And if the movies actually had the guts to go in that direction it would be amazing. Then, after the Justice Lords take over the world (for its own good!) by the end of the first Justice League movie, the real Justice League --a Batman who doesn't brand people, a Superman who had morally centered parents and really enjoys doing good, and a Wonder Woman who never gave up on humanity--can appear in the sequel to defeat them.