I don't think crypto actually serves much of a purpose at retail. As a customer, what reason do I have to pay for my groceries with bitcoin instead of my debit card?

A CBDC is just a bank account at the Fed with an API. You don't need retail banks anymore if you have one; conversely you don't need one if you already have retail banks.

Banks already have such an account at the Fed, and are getting realtime FedWire soon, and it doesn't really matter that the API involves SFTP'ing ACH files around.

Hmm what would the advantage be then? The Fed is already linked up with US Banks