I don't think it's that simple. Sure, money in a billionaire's possession probably isn't going to be used for consumption, but it's not like that money is chilling in a matress somewhere; it is invested. Those funds are a source of capital for public companies, seed funding for small businesses, VC investments for growing companies, charitable contributions potentially, even funds for countries through bonds etc. I'm going to stay away from making pronouncements on how this money ought to be used; I'm merely pointing out that the situation is more nuanced than how you have framed it.