"... increasing a team’s hours in the office by 50 percent (from 40 to 60 hours) does not result in 50 percent more output (as Henry Ford could have told them). Most modern-day managers assume there will be a direct one-to-one correlation between extra hours and extra output, but they’re almost always wrong about this. In fact, the numbers may typically be something closer to 25-30 percent more work in 50 percent more time."
From about 1/3 down in the "The Overtime Exception" section.
"... research shows that knowledge workers actually have fewer good hours in a day than manual laborers do — on average, about six hours, as opposed to eight."
Motivation to build what you really want to build is completely different from being motivated to work for a salary to avoid starvation and keep your family going.
I imagine it's a lot easier being a doctor who is actually helping individual people squeeze in one more patient, vs. spend overtime filling in paperwork. Same difference between working on an awesome product where you have total visibility into the whole process, vs. beng a cog in a much larger wheel.
I work at a small programming company where gratuitous overtime is the norm as a project closes. By the time things calm down again, we're so stressed out that our productivity probably falls by 50% or more for weeks to come. And the cumulative effect after years of this is even worse. I don't think the boss (also an overworked programmer) has yet to come to appreciate this daunting reality.