Why do societies allow billionaires to exist?

There’s almost no common sense reason why an individual person could possibly need more than say $50 million to meet all of the material needs they could ever want.

More than that, and they start to have enough resources to lobby and destabilize society.

So - why? Why do societies even let people get this powerful, there’s no prosocial benefit to it and a ton of risk

Edit: Funny that a lot of the comments are directed at why billionaires should exist, rather than at why societies allow them (which is the question at hand)