If you by "physical money" refers only to metals and bartering. It's all about control, not about the medium. The world is changing and physical stores are disappearing in favor for online markets. Same thing happens on the black market, whether it's outright illegal stuff, or simply stuff a tyrannical government don't want you to have, like guns.

At some point you will have no other choice than digital payments, so the question is. Will you use "their" tyrranical system where you have no privacy, no control and no security. will you try physical, such as "cash or gold by mail", knowing very well that the delivery man could easily rip you off and disappear.

Or will you use a privacy focused cryptocurrency, such as Monero for instance, payment arrives instantly, no tracking, nothing to block your transaction. And the only thing you'll ever have to worry about is if the seller is honest and send you whatever you purchase, which would have been the case either way.

The governments wet dream is about control, not about the medium. They don't give a fuck about medium. If Chickens could speak and happily would rat you out for a few crumbs of bread, the government would use live chickens as currency.