You work to make money, which you need for everything essential to living. Food, shelter, the bottom half of Maslow's pyramid. Fundamental Capitalism.
Some people are satisfied there. Or you can work to save money so, eventually, you will be able to stop working, and live off the savings. Maybe provide a head start for your kids. Most of us would be happy stopping there, and good luck to us all.
If you're lucky or ambitious or aggressive enough to speedrun the process, and already have enough money to never have to work again, but still bust your ass to acquire more, what's the goal?
It takes considerable effort and intelligence (and usually a head start) to enter the ranks of the .1% – so why is all that effort put into acquiring more than anyone could ever use or even give away? Continuously making deals and acquisitions, taking risks that might pay off, but might bankrupt you – that's not easy.
Someone with that much money and power that just uses it to get more money and power – is that the end goal? Is it all part of attaining immortality – never being forgotten – look at my pile, ye mighty, and despair?
Is the end goal acquiring power and means enough to do or have anything you want, pursue your wildest dream without limits? There are people with that amount of money already, but it seems the dream they are pursuing is just getting more, by any means.
Maybe I'd be a shit billionaire, but I just don't understand the motivation.