It is, unfortunately, completely sustainable. I used to be a great friend of cash, but with automatic cashiers everywhere and a Garmin watch that you can import your card into, I don't even need to carry a wallet if I just want to buy a few apples. And Covid introduced card use to many people who used to be reluctant about it. (The older demographics, which was most threatened by severe disease.)

I still realize all the privacy and civil rights ramifications etc., but cash is slowly becoming an equivalent of steam engines fighting against diesel and electricity on the railway; high maintenance and inefficient.