Digital payments aren’t something that is alien to a large percentage of the population. Credit and debit cards are being used more and more over cash. Even payments made electronically are becoming the norm. Services like Apple Pay and Google Wallet allow customers to pay using NFC by passing their phones over card machines.
It’s not that far a leap to a future where all currency is digital. I think the question is one of security. Or, at least, the perception of security. More and more news stories are cropping up about hackings and network security that serve to scare the public out of trusting technology.