There's a problem, though. We're talking about idling the populace for half their time, then denying them the resources to take advantage of the slack. - Wanna focus on your music? Hope you like ukulele. You've got enough to cover your basic needs but beyond that, you're saving up for a long time. - How 'bout travel? Well, there isn't a lot of funding in place for that. Keep it local, keep it fuel efficient. Air travel is largely out. - Cooking? Well, your recipes are going to be heavy on basics. A part-time world is not one for gourmands. - There will certainly be a lot of Khan Academy bullshit - idlers sitting on their Ikea furniture learning skills that they hope to apply, finding out about things that interest them. But considering we're basically making everyone take half a job - purely because we want there to be enough jobs to go around - means that actually applying those skills is going to become a sticky issue. Otherwise the whole "21-hour workweek" becomes a farce. This is pretty much Marxism-Leninism, which did not exactly work out. There is an innate human need to strive and whacking it off at the legs and saying "thou shalt not work hard" only frustrates. Far better to make sure that everyone's needs are covered, everyone feels fairly compensated, and everyone gets a chance to excel. I work shit-tons of hours at two or three different careers. It doesn't wear me out at all. But then, I haven't been inside a cubicle since 2007. That shit's a grind. I think you'll find that the lower-class fast food worker will happily put in 50 hours a week if it means he gets a roof over his head, a way to get to work, safety and security for his family and the resources to enjoy his leisure time. I also think that if you make the coder or researcher or engineer or machinist put down his tools for more than half the week, he'll find black-market ways to thwart you. People are happy when they're busy being fulfilled. The problem isn't the excess of "busy" it's the dearth of "fulfillment."Naturally, it takes a shift of mindset among people to place a higher value on leisure than on prestige.
However, if we recognize it as a benefit for society it could be encouraged and worked towards, just like ever increasing consumption and demand was encouraged during the 20th century as a political and economic tool.