I think you're right about online fraud being much reduced with public private key tech, but if it's such a good idea why has no one been able to do it?
the IMF has no incentive to change the way it's doing things & would require a 'rewrite' of the current infrastracture. Also, public/ private key encryption is not quantum-safe, so eventually we need another way. (There is ton of research being done on quantum-safe cryptographic proofs)
History shows systems rarely 'change'. More likely than not they are replaces. That's what BTC is an attempt at.
