Probably none, though I'm putting words into their mouths. Many seemed to be looking for the mentoring, "office next door to <X>," and team aspects as well. Modulo health insurance, many of these people probably didn't really need any income at their wealth levels.

Extending that, a huge number of people I worked with at MSFT were quite wealthy and just hanging around because it (developer divison) was a fun place to hack. I think the biggest cause of retirement was reaching that point where the children head off to college and the spouse wants to move someplace less dark and dreary.

But, my experiences are certainly not a representative sample of the population!