So when you've earned your f-u money you stop showing up for work?

That's not what we see in practice. Most people with a sudden windfall (stocks, lottery winnings etc.) keeps showing up for work. Because how else would you stay socially meaningful in our society? Nobody really wants to sit at a beach sipping drinks the rest of their life, accomplishing nothing.

There is clearly a social aspect of work, at least for the majority that we can call socially functional. And it's at least as important as getting paid. Work is also a social role, and it hurts many people if they are left out of it. It's not easy.