[grondilu]

When you exchange coins physically, the payment method is ... your hands.

> bank credit has more recently become treated as currency

A bank credit is not a currency. The thing it is denominated into (EUR, USD, BTC...) is.

> And of course the reason bank credit has more recently become treated as currency (sic) and accepted as electronic payment

I think the real reason is that people had little to no choice in that regard.