This has happened in China with astonishing speed over the last few years. Back around 2012 every thing was all cash, all the time. Now, even the tiniest vendors accept WeChat Pay or AliPay for everything. Everybody has a mobile phone and they use it to pay for taxis, restaurants, convenience store purchases - everything that would have been cash-only just a few years ago. Just scan the QR code and go.
If China suddenly decided to ban cash, they could now do it overnight without inconveniencing anyone (except gangsters) in the short run. It would annoy all the grandmothers with tens of thousands of RMB stashed in coffee cans, but daily commerce would be unaffected.
Americans have not adopted equivalents like ApplePay as quickly, though we do love our debit cards. But they are going to try something like this Chicago Plan the next time Democrats control the White House and Senate. It will greatly help the Deep State foil political upstarts like Trump in the future.
This system was already obsolete before it was implemented.
In China the WeChat and Alipay and I believe several others can be called up by the McDonalds ap such that you enter your order on the McDonalds ap and press the button. The order is entered and you are given a number or perhaps a name that can be called. On delivery, the order is processed backward to gain payment by the above named service.
Your phone can hold aps for McDonalds, Pizza Hut, Chick Filet, Walmart Target and on and on. Such abilities are I've read ubiquitous in China and are the accepted norm for buying many many things.