It takes far less money than a billion dollars be able to make world-changing charitable donations. You could, say, fund a light rail system (yes, even in a decently-sized city) or housing for every homeless person in your home town for vastly less than that.

There’s only so much you can invest in yourself and your personal hobbies before there is nothing more you can realistically buy. Any normal, reasonable person, once already confronted with a luxurious lifestyle for themselves and their loves ones that will last forever, looks at all their extra money and decides it would make them feel good to make those world-changing charitable donations. And so they do it.

I’m sure everyone’s point of balancing anxiety and lifestyle is different… but any reasonable person, it’s WAY before they hit a billion.

In short: a normal person starts wildly giving away their wealth long before they become a billionaire. You have to be some kind of antisocial weirdo not to.