Like I said - you can go minimal staff, cashier-free transactions and still take cash in your store - the checkout machines already exist.
And I didn't say things aren't going this way - it's been the trend direction since Amazon pushed the electronic vs. brick and mortar divergence out there (I'm sure you've seen the checkout lines that say "No Cash/Checks." for years). And it's not just in the retail space. An area where you can really see how this is playing out is in the parking meter space. The desire to reduce/eliminate cash at the parking meters is probably several years ahead of the retail space here, at least in terms of scale of implementation. Anecdotally, I knew a guy who ran a company that digitized the parking meter space in his city, this was 15 years ago. They went with a targeted card model (which had an acquisition cost to the user) and tied it into the public transportation system as well. Of course, the money is made in the transaction premium, blah, blah, blah, I know that you can work out profit models on your own. Anyhoo, my point being that this isn't new and we're not moving in this direction, we've been moving in this direction for a long time already.
What I said that a municipality has a responsibility to ensure that cash is still accepted within its jurisdiction. A single cash-free business here and there isn't a big deal. A city's problem is when the majority of its businesses adopt that model. Then you run the risk of shutting out your poorer citizens.