Once you have enough money, you realize there’s more to life than just money. Philanthropy is a way to help make society better, to give back in ways in which the government is unwilling or unable to fund. For some, it’s a way to get recognition from their peers, but many give anonymously, trying to maintain their privacy.
My view is coming from an American’s perspective. I expect many other countries have less generous philanthropy traditions.
Now, why are Americans such large givers to charity?