They don't though, they "donate" to their OWN charity which is then controlled by their children... Virtually none of that vast wealth actually goes to helping people.
It is simply a tax evasion technique for them.
Side note: this is also why many professional athletes have "charities", they learned from the billionaires.
Money, it was huge in the nineties to build golf courses lined with houses.
Some people who bought houses loved golf, they usually got many perks at the course. Some thought it'd be cool and didn't think of the double-sides.