The instinct to acquire resources does not have a limit. When homo sapiens evolved, such a limit would not have been a useful adaptation. There were no billionaires then.
Also it's nice to boss people around, probably for the same reason.
You and lots of people say would do something or other. I submit that it's different when you're actually in that position, as opposed to imagining it. Lots of us imagine we're going to go to the gym for years, and give up after a month or two.
Some people have made the (good in my opinion) point that this is actually survivorship bias and a lot of people actually do retire and are never heard from again once they have enough money. So people predicting what they would do aren’t necessarily that wrong, it seems that some people actually do that.
Also it's nice to boss people around, probably for the same reason.
You and lots of people say would do something or other. I submit that it's different when you're actually in that position, as opposed to imagining it. Lots of us imagine we're going to go to the gym for years, and give up after a month or two.