Philanthropy
The giving away of money or stuff.
Sounds so simple, but through the gauze-filled lenses of tax and estate laws, it's so much more complex. Start with the idea that, after you have, say, 3 homes and a jet and maybe a boat, there really isn't much else that you'd want that you can't just rent for a weekend way more efficiently. So...the price tag? Maybe $100 million? $200 million? We live in a world of centi-billionaires, so there are a whole lot of truly wealthy philanthropists above that "baseline" unit or two of wealth.
The question then revolves around how they gave away the rest. Yes, they'll pay for their kids' and grandkids' educations, buy nice toys along the way, etc. But the total cost of that stuff? Tiny. Almost rounding errors in the scheme of wealth. Take the "average" billionaire. Tens of thousands of them around the earth now. They have $200 million for toys, and the remaining $800 million is left. If they gift to their kids, they'll lose about half to taxes. If they gift to their grandkids, they'll lose about 75% to taxes. So then...why not just give it away to a charity you actually like rather than handing it over to government people who are, for the most part, morons, thieves, and/or people we just wouldn't want having our hard-earned money "for free"?
Gift rather than tax. That's the gist, anyway.
In the modern era, most wealth is contained in shares of publicly traded companies; i.e. in the old days, wealth lived mostly in the form of arable farmland and/or gold stores and/or water rights and cows and stuff. But today, a given company founder has a cost basis of, say, a penny a share in a stock trading at, say $100 a share. So almost all of that $100 is taxable. If they sell it and they live in a Blue State, they'll keep $60 a share after taxes. Then, if they want to gift that $60 to their kids, taxes will take another 40%-ish out...so it turns into $36. Then, if it's to go to their grandkids, post the generation-skipping tax, it turns into $24 or less. So yes, that original $100 in stock becomes $24 by the time it gets to a destination you'd care about. Or said another way, it costs you and your progeny $24 to give away $100.
And this is where the precepts of philanthropy begin. Do the math after you're a unit or two wealthy, and it fast becomes easy to understand why we have such nice statues at private universities.