Because "charity" is not necessarily the best place for them to put it. Lots of money goes into charity, but a lot of it is lost from inefficient spending.
And few of them believe their businesses are not doing a lot of good for society. Jeff Bezos is the only one who can create an Amazon. Rockefeller improved transportation. Warren Buffet invests in businesses people are too greedy or impatient to invest in.
They all believe that they're adding a lot of value to society by doing what they do. Elon Musk is good at articulating what he does, but Jeff Bezos probably believes that he's doing a lot more good for poverty in the USA by reinvesting his money into Amazon.
And few of them believe their businesses are not doing a lot of good for society. Jeff Bezos is the only one who can create an Amazon. Rockefeller improved transportation. Warren Buffet invests in businesses people are too greedy or impatient to invest in.
They all believe that they're adding a lot of value to society by doing what they do. Elon Musk is good at articulating what he does, but Jeff Bezos probably believes that he's doing a lot more good for poverty in the USA by reinvesting his money into Amazon.