He does, it's literally what the Gates Foundation is for. It isn't easy to just give away $100,000,000,000 and trust that even half of that will get meaningfully spend and that it won't actually wind up getting abused by assholes in powerful positions and making things worse. That's $14 million per day for twenty years.
That's a great strategy if you don't care where it goes. You'd probably be surprised how quickly money can disappear when you have people motivated to spend it.