So does handing over a physical wallet.

Also, nobody quits MasterCard et al because it relies on the internet...the transactions are cached, and the few problems when things come back online are dealt with as a standard "doing business" item — everywhere from insurance agencies to corner stores.

I do carry cash for when mastercard is down. Because I tend to get in a bad mood if I can't eat due to internet issues (or any other issue).

So does elliptic curve signing, radio, digital storage. Confirming a transaction in this state would probably be competitive with making change for, verifying, securely exchanging, securely transporting and securely storing gold.