Cash will have relevance as long as internet and cloud failures are still an ongoing thing .. both for lovers of privacy and viable fallbacks as required.

Of interest, today in Australian media:

Why cash has made an unexpected comeback in Australia: new study - https://theconversation.com/why-cash-has-made-an-unexpected-...

which includes figures that show while only 8% of Australian transactions are cash (by some metric, see article) 33% (a third) of the population fully supports keeping cash on.

And that is fine and I do the same.

In Germany in many places you can only pay with cash.