Comic books were cheap entertainment for kids; as were the Saturday morning serials where comics characters were first adapted for the big screen.
Eventually, though, comics creators began pushing the boundaries of what superheroes could do and say, and before long their movies began to follow suit as well.
When superheroes were first created, they were intended primarily for children.
If you still believe that comics are just for kids, any of these titles will disabuse you of that notion immediately.