I agree that Jobs and Apple have always had the attitude that they had the better product but just didn't have the wide-appeal that MS has had (until recently). But if you look at Gates, he is the richest man in the world and built the most powerful and biggest software company (for a time). What else in his career is there to do? Nothing. He's come to the correct realization that there is more to life than competition and money and now is going to focus on helping people.
Gates gets a lot of flack, but not the credit for the good that he does outside of the tech community. He is a bully, but he could easily stick around and try to crush linux and Apple - but he's rightly moving on