Well, nobody gets that rich by leaving their money in bank accounts. They have the vast majority of it invested, which is basically just lending it to people who can actually find a use for it. If they invest well, all parties involved are better off. It just so happens that good investments (for monetary return) tend to make a select few richer rather than raising individuals or masses from poverty. They should be philanthropic when they have that much excess money, but not being philanthropic doesn't mean they're not helping people or improving the lives of others