These people don't make an active choice to give their life to the company/firm. It's a series of small decisions that add up to a huge sacrifice. It's like boiling a frog. Nobody ever says when you sign up, oh, you'll have to skip Easter Dinner because you can't afford two hours off that week.
The trick is to create a culture where it is not only normal, but taken for granted, that you work all the time. They work with a bunch of other smart, capable people. They can't all be wrong can they? (yes, but it's easy to see why they can't see it).
So the mechanism of the slave driving isn't just someone sitting there telling you--work 100 hours a week or you are fired. It's by assigning you almost unlimited work and having a competitive environment where you look bad if you can't complete it.
So these people become their own slave drivers. They stay at work late without having to be asked. They make the choice themselves. It's a sick culture, but it makes their stockholders money. You actually feel bad when taking time off because you feel like you are falling behind.
Part of it is definitely the striver culture that elite education often encourages. You are supported to give full intensity and take any abuse to succeed.
However, I wouldn't write off all people like this off as sheep. I bet you'd be very surprised how you react under similar pressures. And certainly some tech companies employ similar tactics and have similar cultures of encouraging people to give 100% effort.
Another big factor in these sorts of jobs is that it's view as a temporary hardship. You do a stint and exit into the "good jobs" that aren't this insane. That causes people to try to tough it out. And they end up breaking before they bend.