I remember this being dealt with in quite an interesting way in the first arc of Morrison's JLA with the White Martians. They showed the extent to which the world could be changed if super humans intervened more to 'help' humanity, but there was a strong implication that that level of intervention would do as much harm as good.
(That story copped out a little bit on really answering the question by revealing the White Martians as bad guys, but it was an interesting question nonetheless.)
On the other hand though, I see the sense in not letting it be a question that's asked too loudly, or it can call into question a lot of other superhero stories that try to balance powerful and super-intelligent beings with a 'world outside your window' setting. (Like why the Marvel Universe isn't an utterly transformed place in terms of science and medicine, given the genius of people like Reed Richards.)