Aside from AWS, who's famously bad at this, my experience is that this is usually because people want a faster career push.
Imagine Jim, 8 years into his career. Jim is pretty good and his work takes him 30-40 hours a week. If he worked another 5 years in the same role it'd probably drop to 20 and be chill.
Jim wants to get promoted. If he waited the 5 years he could do it working 40 hours a week. But he wants it now, and since he's not as good as he will be he needs to work 60. What does Jim do? He works the 60.
There's nothing wrong with this choice, I made it, I'm happy with my choice. I might make it again in the future, or not.