That works with the current banking system as well. That's what made the Nigerian scams so successful.

Yup, but the current system is not a decentralized, immutable database.

At least you kind-of-sort-of have a chance at reverting a transaction.

Heck, my bank completely blocks my transactions over a certain limit (I need to ask for temporary limit increases through a separate process) and frequently delays transactions larger than another limit and they call me to verify that I want to do them.

Sure, blockchains could do the same, through intermediaries, but then... they've reinvented banks.