I was VP Eng of a 40+ person team at a startup, and my workaholic CEO once asked me if it bothered me that other people on the team didn't work as hard as me. My answer was very tactful, but noted that in any decent exit, I would walk away with multiples of some of those people, so it made perfect sense that I'd work harder.

But it is not only about the money. People just have their own lives, interests, and passions. For me, the lack of autonomy when doing my job kills a lot of the motivation.