Here is a funny thing...
If $100 dollars is kept "digitally" and only processed through the banking debit card system, after 3,333 transactions that $100 will be all sitting in the bank as their profit. Every time a transaction is made, the card processor takes 3%. That $100 is no longer currency in circulation.
If 100 dollars is kept as currency and spend over and over again, that $100 will still be able to purchase $100 of value. That $100 stays in circulation.
This is why banks want to be all digital. They take a cut on each swipe.
Cash and debit cash are different mechanisms at play.