Hi All, As I finish yet another trashy scifi space opera , no...

Hi All,
As I finish yet another trashy scifi space opera , no cash ever used.
Personal transactions all seem to be chip to chip.
ie , not requiring immediate use of a bank
So what are the technical , or any other obstacles to such peer to peer , digital cash, using a phone or active card?
cheers

Now , I am perfectly happy for cash to continue, I always have a couple of hundred in small notes .
I am perfectly happy to pay a fee for its use , happy to pay a fee( direct or indirect) , just as with tapping.
I would object to subsidising the use of cash , and mandating its use inevitably causes a subsidy.