That's funny. I remember when Americans travelled to Europe, we were strongly advised to bring cash because plastic was not nearly as widely accepted.
That's a misnomer, you still should bring cash. It's not that plastic isn't widely accepted. For a long time it's actually been more widely used in Western Europe than it has been in the USA. It is *CREDIT CARDS* that are not widely accepted (and still not in much of Europe). Most of Europe runs on debit transactions. Yes it can be confusing to see two overlapping circles and confuse the Mastercard logo (red and yellow) with the Maestro symbol (red and blue) or the Cirrus symbol (light blue and blue).
Come here with your fancy Mastercard / Visas and you may not even be able to buy something at a major supermarket even in a very digital country. And god help you if you have an Amex card.
That said things are changing Mastercard has announced it will discontinue Maestro and that is forcing countries to massively rollout card readers capable of reading Debit MasterCards and VisaDebit cards, and since they have the same underlying technology as credit transactions, that will mean credit cards will very soon become far more widely accepted.
Reminiscing aside, I don't see a need for a mandate. If enough people complain, I'm sure charging makers would include credit card readers.
This is a case of a captive audience. If in general machines don't accept credit cards then the complaints will fall on deaf ears. What are you doing to do, drive to a different supercharger and hope for the best? Call roadside assistance when your battery runs out? It's one of the situations where you get to force your customers to do what you want.
TBH, what'd I'd prefer over either a phone app or a credit card is that plugging your car in looks up an account and payment method and just handles it (which, I believe, is how my Tesla-owning friends tell me it works).
That is coming. Quite a few cars on the market support auto-negotiation of the charging. It does work for Tesla... at Tesla chargers. Great if you have a monoculture, not so much if you live in Europe where there are literally close to 100 different companies offering charging infrastructure.
That said most of them offer "network" style subscriptions, which is to say you apply for something like a Shell Charge card and you can tap and go literally anywhere. Yeah it would be nicer for the car to do that automatically, but really you need to stand next to the charger to plug the cable in anyway so it's not like tapping your charge card at an RFID reader is a hassle. So far I've yet to find a single charger that didn't work in my "network" of allowed chargers.