College does not qualify as ten thousand hours of practice of anything, except maybe note-taking or socializing, and this is probably why most people are not great at anything when they graduate. With all the “general requirements” and electives students take, they don’t spend anywhere near ten thousand hours practicing the field they major in, unless they’re practicing outside of classes. You can’t rely on college to give you the ten thousand hours and automatically push you to the top of your field. It can help to an extent, but, like you said, people like Gates succeed without college because they practice on their own, and there is no replacement for that.