Is there evidence that it happens? And that it serves the public good, not the personal interests of the wealthy? Do we need another $100 million given to a health program accessible only to the wealthy, or funding for public health? To a business school or art museum, or to arts programs for public schools?

Philanthropy is anti-democratic; the people don't choose what is important to support, the wealthy few do. You can see that in the relatively poor public goods in the US, which has much lower taxes relative to peers.