[P_I_Staker]

So, I'm not going to say this is definitely the reason, and there's no way around it currently, but this is partially a function of a competitive work environment. Someone is bound to be willing to put in the time, or the threat of it will keep people from exploring (demanding) progressive things like 25-35 hr workweeks.

On the edges, where people are forced to work 60+ hrs a week there's enough leverage of people simply being unwilling to do the job (though even this isn't as true for some elite jobs). On the other hand, if they're just being asked to clock in from 9-5? There would need to be some outrage and push, but this makes you look lazy. There seems to be some progress made on vacations in corporate America, though.

Also, some roles would legitimately suffer or not work at all at 20-30 hrs. I think the ideal is to normally work 40-60 hrs "busy weeks", but not try to load people down when things naturally get slower and let them dip into the time for personal, so it's usually 30-35, or occasionally a bit less.