A lot of these people have ambitions that require a lot more money than that. Maybe they want to cure aging or explore space or something.
Another way of looking at it: if someone makes 100m a year and they are thinking about retiring, how much would you need to offer for them to choose to work another year instead? That's how much you need to pay them next year.
Certainly there’s a vast range of FIRE styles and even what constitutes retirement but at some level it’s a combination of keeping score, feeling valued relative to peers (see also sports), and the industry recognition.
Most people have egos. Some more than others. And public recognition via titles matters a lot for future opportunities. (Though maybe you don't care much about that so long as you make enough money.)