First, your wealth is not secure. You can be sued by disgruntled shareholders or employees or customers, and your assets may be at risk. You are a target for litigants.Second, if you try to sell these assets or cash those dividend checks (for Facebook, non-existent at this point) you will have a huge tax problem.Third, you might want a way of passing on riches to your children, while avoiding the Gifts and Estate taxes. A nice seat on the board of your 501(c)(3) non-profit is a nice way to send them a regular paycheck, without inheritance taxes to worry about.Fourth, you might want to polish your image as a "nice guy" and a charitable dude, which in turn would help your business.
Fifth, you might want to influence the government to enact laws in your favor, and doing this directly can be messy and difficult.
Sixth, the whole point of having Billions of dollars isn't to build a house of solid gold, or buy the world's most expensive car (indeed these things cost mere millions) but to control other people or even society which is indeed the primary function of money.
"There is also this to be said. It is immoral to use private property in order to alleviate the horrible evils that result from the institution of private property. It is both immoral and unfair."
In other words, is it really right that Capitalism should concentrate power and wealth in the hands of a few - who in turn toss us pittances in terms of charitable contributions, and then expect us to laud them as rock stars? They throw pennies at us, hoping we spend dollars.
That ain't the case. A "non-profit" 501(c)(3) corporation is, as the name implies, just a definition from the tax code. No more, no less. And that is all.