I'm not sure how they can be considered to be doing much, or any, good, when effectively they are passively siphoning off profits and despite all the "good" they do, as a class they get rapidly richer every year. That has always been a conundrum behind Bill Gates' charity. Of course, it's not really a conundrum. The charity is just tax-advantaged PR or tax-advantaged complementary investment masquerading as goodwill.
It's all arbitrary, IMO. Idk if they're "siphoning off profits", since most of their value is in equity and Amazon, for example, isn't historically very profitable.
Getting richer every year in equity value is a strange concept. I think there should be some additional taxes, but we also shouldn't expect taxes to be a real solution.