The homework has to be just easy enough that every kid can do it, which means that for many kids, it's mainly a test of focus and motivation. This is all the more prevalent today, when homework has turned into drill work for the questions on the standardized tests.
I've got two kids, and so I can attest from limited anecdotal evidence, that it's completely unpredictable how each kid will relate to homework.
I am curious, is this about some particular kind of homework? From my own experience, I would think that exercising a subject alone (which is what most homework was in my school system at least) is a very good way of understanding it better. I of course remember not wanting to do homework many times, and I remember excessive or idiotic homework assignments, but overall homework seemed to be one of the major modes of learning for me.
Also, related to Gates, Page, Brin - I don't generally think that it's a good idea to look at a small number of very successful people and try to emulate some part of their life experience - you are, în general, very likely to fall for some kind of survivorship bias, or accidentally home in on a less important detail (for example, Gates was probably helped much more by his extremely wealthy and well-connected family than any particular aspect of his schooling).
On the other hand, there are many voices saying that one of the important purposes of the public education system is to engender conformity, which is very rarely conducive to a truly out of the ordinary life. Noam Chomsky would be one of the most credible, and he has often credited his own career to his non-standard early schooling.