UK has instant payments between bank accounts too - no fees to cover fraud and fraud is covered.

UK isn't a good example since they don't have fraud protections in place. This bill needs to into effect before the banks are on the hook. https://bills.parliament.uk/bills/3326

Most banks are signed up to the "Authorised Push Payment Scam Code" and cover fraud, however it's not a legal requirement.

But all banks, of course, have a level of fraud protection in place (just not the legal obligation to replace funds from a scam and compensate/reimburse victims).

It's also worth noting that this is a legal decision, and not a technology issue.

They reverse the payment when law enforcement gets in.

And what if the money is gone by the time law enforcement is involved?