I'll give a different answer, which is that a blockchain-based prediction market can be used as an oracle for other blockchain-based contracts. So there can be both a final answer and a mark to market for the contract which should approximate reality in some way. However, being unregulated, there's always the possibility of cornering the prediction market and causing the derivative contracts to end with unreality. So you may need another kind of oracle to finalize the market price of the prediction market.

Probably could be accomplished without crypto, but it can also be accomplished on some blockchains with minimal additional investment.