I also think it is noteworthy that actual cryptocurrency exchanges exist to get around the limitations of blockchain-based settlement. It’s hard to short bitcoins or buy bitcoins on margin, which is why exchanges exist and use off-blockchain methods (lending you money, keeping custody of your bitcoins, etc.) to allow you to do those things. (Sometimes that’s a mess!) It’s not like you’re using the blockchain to buy bitcoins with dollars on a cryptocurrency exchange; you’re using your credit card. If you want to rebuild the regular financial system along blockchain principles, you have to wrestle with the fact that even the bitcoin financial system doesn’t really operate on blockchain principles.
That is from Matt Levine.