Why doesn't crypto have prediction markets yet? (Yes, I know Augur and Gnosis)

[ranreichman]

Theoretically, all you need for a prediction market is a smart contract with a seller, a buyer, and mediators. Why can't I use an Ethereum smart contract to bet against someone on Wimbledon (for instance) and have 3 agreed upon mediators who get a small commission and decide who won the bet? Seems simple so I'm probably missing something.