It is Musk's company, his choice. I made the same for my company. Relevant experience and attitude are just as important.
Regarding college, Musk is an entitled rich douchebag whose parents own half an emerald mine. With that kind of money, you can just fuck around at college. You know you'll be all right. For those of us without wealth to back us up, learning so that you could get a good job and live on our own was not an option.
Don't get me wrong, I had a lot of fun at college, too. But busting my ass to get into engineering honors societies had a higher priority than beers and bongs.