It makes sense for the banks to do this, because they have different requirements.

Bitcoin is great because it works with an unknown set of untrusted entities, and there's no counterparty risk because the ledger is the currency.

Banks have a known set of semi-trusted entities, and want to track off-chain assets. They'll still have counterparty risk, but if they see a way to use chained blocks and something like Byzantine Paxos to speed up interbank settlement, more power to 'em.