But they don't have to be perfect, they just need to be better than what currently exists.
ACH and SWIFT are, at their very best, mediocre and sad when technologically compared to blockchain.
In fairness though, if all transactions made it into a blockchain, fewer and fewer people would be able to store it in their computers, let alone process it.
Quite the contrary. Modern banking transfer technologies are much better than Bitcoin at what they do. They're orders of magnitude more energy efficient and also much faster than waiting for blockchain confirmation of transactions. Banks are usually quite bad at exposing that functionality to clients but the actual technology beats Bitcoin easily. That's not even surprising. Sending a few messages over the internet and updating a couple of database registers is massively simpler than running a distributed PoW ledger.
And here are those technologies properly exposed:
https://play.google.com/store/apps/details?id=pt.sibs.androi...
Immediate transactions between individuals in the traditional banking system.