996: 9 a.m. to 9 p.m., 6 days a week

Sure, they're burnt out, sluggish, surly, but... they're present. And when they're present, they're not out in the world spending their income. They don't need an expensive apartment or house, all they do there is sleep. Why have a fancy car when all you do is drive to/from your shitty job in it? Family? Who would have children with somebody who works such a schedule?

Even if you got more productivity from the same workers on a 9 a.m. to 3 p.m., 4 days a week schedule, you'd have to pay them more, not just per hour but overall, because they'd be out spending money on those afternoons / evenings and 3 days a week they have off. Organizing, demanding better healthcare, dental, more paid time off for vacations, and higher total wages to support all these "needs" they invent for themselves on their time off.

Keep 'em locked down, keep 'em tasked with ... anything, doesn't matter if it's productive or not, as long as it keeps them on-the-job and not spending their pay.

Edit: apparently this isn't clear: 996 is a horrible idea from all perspectives, it's bad for the workers and bad for their employers overall. But, in certain twisted views, it would be a bit like military service where the (bulk of the) workers get a pitifully small paycheck, but they don't have any real expenses so they have the option to save it all. 996 would turn that more into a wage-slave implementation where the pitifully small paycheck is just enough to meet their pitifully small expenses. In the China tech sector where they have implemented this (it is now illegal, but still practiced) they also do things like install anti-suicide nets in the stairwells of the highrises the workers work and sleep in.