imagine you have a smart contract that says A promises to pay B X when they complete task Y. If task Y is not representable on-chain, how do you execute the con

imagine you have a smart contract that says A promises to pay B X when they complete task Y. If task Y is not representable on-chain, how do you execute the contract? How do you certify that the thing Y was done exactly as expected? There are very few meaningful things that you could slot in for Y that would not require some kind of out-of-chain verification. Say B says I did Y and A says, sorry, you didn't. How does B get their money, etc. They need courts, notaries, trusted fiduciaries. At which point, why did you have a smart contract anyway?