The issue with people saying things like "He could have used those billions to end homelessness in America" is that it assumes you can solve systemic, ever-present problems by just throwing money at it. There's a whole lot of complications to why people are homeless and why there's so many hungry people despite the world having the resources to feed them all, and just throwing money at NGOs or individuals isn't going to solve the entire issue. I get the sentiment: billionaires could use their money for much more worthwhile goals, but you have to understand that the world doesn't work like that.