If you're anywhere near as old as me, you'll remember devaluation and the assurance we had about "the pound in your pocket". It couldn't happen now; I mentioned the pub in Chester which has a notice on the door saying "Cash only"; it was my son who said it was designed to keep young folks out.
You may have noticed in some places people buying a cup of coffee by showing their phone or waving a card about. In a growing number of places it's cash that isn't accepted; cash can be more expensive for businesses to handle; it's bulky; it has to be counted and stored securely whereas digital cash cannot be stolen and is already in the bank.
I'm afraid we're still in the stone age; we don't have the right apps on our phones for waving. I still have a cheque book but a diminishing use for it.