Here's a partial explanation - a contributing element.
Do they have an option for working shorter hours at the same hourly rate? I suspect not (employers will much prefer those willing to put in long hours once the tradition is in place). So people who want to make a lot of money have to work hard now and plan to switch to a lower paid job once they've saved enough. But switching to a lower paid job (or stopping working for profit if you're rich enough) is psychologically unpleasant and culturally discouraged, and people will keep putting it off. Or it may be hard psychologically to live modestly while making a lot of money.
This is effectively why my mother claims to have quit her veterinary practice: she didn't want to keep working 70 hours a week and she couldn't do it as a 9-5 job.
Such situations probably aren't due to a widespread evil "tradition" among employers, but rather due to the fact that a skilled worker's average productivity-per-hour is typically maximized at a high number of hours-per-week. Any medical professional, for instance, needs to spend many hours per week just keeping up with advances in treatment options, changes in regulations, etc, but overhead hours are wasted unless they're amortized over even more hours spent actually administering treatment.
The other day, someone did something I didn't expect. It was something many people have done before; something that I thought of as very normal, but that I in no way understood and had not predicted.
As I said, this had happened many time before, so I wrote it off as "me not understanding people" or "people are weird" for a second, like I usually do, before realizing that "bad at" really means "lacking basic knowledge", which I had never realized before.
And then I thought "I should ask someone who is different from me why people do that, and eventually someone will have an answer."
But many people will have many more questions like this. So, what have you observed people doing time and time again, but never understood? Or something that you only understood after a long time or asking someone about it?
And can Less Wrong tell us, not necessarily why (I for one can make up evolutionary psychology fairy tales all day if I want) but what conscious thought process occurs behind these events?