In China, even though the gov said that it is illegal to refuse using the cash. Most of the small shops stop receiving that. They do not have enough cash to give change.
As for me, the only problem is that when your phone is dead, you can barely purchase anything. So I always carry a credit card.
I do have some cash at home for emergencies. But it was already locked there for several years.
The only reason when you need cash would be that you want to "hide" the trade. The police has already cought a lot of drug dealers by tracing the payment records of their customers.
However, as most of pepole will not use cash. So it will be much more easier for police to trace the serial number of the cash. It is getting more difficult to
"hide" payment these days.
Not only for drug dealers, also for the husbands who wnat to have some small private money. Especially when you want to buy some games or some new useless gadgets. You will miss the good old days with cash.