There are people who actually enjoy working 12 hour days. My brother is like that. Not working makes him miserable. If he's not bashing his head against some difficult problem, he isn't happy.
Hey, just wanted to say I feel incredibly lucky our species has developed such diverse individuals! I think we need the Elon Musk and your brother types, as much as we need the more relaxed family oriented ones. I think it's a shame if our society develops a stigma either for one or the other type.