You are trying to tell me that someone like Warren Buffet with a net worth of $50 billion can really actually make good use of all that money? I know, "there can never be enough" out of principle. But really, with 50bn I imagine you could not (sanely) possibly spend it fast enough in a way where you get something out of it or in return; it would grow back faster in interest than you can dish it out.
Well, assumed you were talking about sums < $1B. I can think of useful (starting businesses, research/engineering projects) things to do with up to $1B or so.
Now, suppose we wanted to cap individuals at say $2B. How would this actually work? That's not cash that's lying around. Almost all of Buffett's wealth is in equity of Berkshire Hathaway. He can't sell that without also losing ownership of BRK. Is BRK worth as much without Buffett and/or the people he's explicitly groomed?
Billionaires are billionaires not because of their income, but because of the assets that they control.
Yes, there are a lot of people spending mega-bucks on what I consider frivolities -- utter waste.
But, there are others starting space programs. I don't want to lose the latter.