Hah. I very nearly posted this a few minutes ago.
It is culturally and economically engrained that people work 5 days a week in 8 hour shifts. Despite technological advances, this is not something that I foresee going away anytime soon. Also, it's hard to picture what an entire civilization would do if suddenly everybody had twice as much free time. I would like to think it would be good, but maybe not entirely so. That said, there are way too many, as Graeber puts it "bullshit jobs". My last job was one, and I hope my next one is not. Busy work for the sake of working, and you have to work it otherwise you can't make a living. It really is a societal problem, but one that's too complex to pin on any one reason.