Perhaps some better informed forumites can explain whether the necessary hardware already exists to allow seamless comms between the vehicle and charger to swap identities? Is it simply a lack of regulation that prevents the transaction being conducted through centralised billing in the same way that the SuC network does? Even if we must have several accounts with multiple companies, that's fine if the billing just happens in the background. Plug in, if you must, make me press a button on the machine to agree the fee but nothing more please!
Standards now exist for how to do this properly (securely) - they didn't when Tesla started. It is standardised in ISO 15118, and has the marketing name of "Plug-and-charge".
All cars with CCS have the necessary hardware for the comms link, as do all DC CCS chargepoints; both lack the necessary software (and in the case of cars, security certificates). There is a possibility for an insecure implementation that works on all existing CCS cars - using the car's MAC address as a customer identifier - and Fastned have implemented this. It's a bit of a distraction though - it can't be a long term solution as it's trivially forgeable, though it works in the short term because the market is small enough that it isn't worth the effort for criminals.
AC chargepoints do not have the necessary hardware - although the standards permit the same comms link as for DC, hardware implementing this in AC points is very rare. Hardware extra cost is modest but not entirely trivial; probably more significant is the R&D effort, certification etc..
Plug-and-charge is likely to appear in DC public charging without much further argument - the car makers are keen on it - but a bit more lobbying wouldn't hurt. There doesn't seem to be much progress towards getting it in public AC charging, where it would be equally useful. There seems to be a perception that because AC charging is a lower value product that all these crappy payment systems can be tolerated and convenient systems (contactless bank cards in the short term, Plug-and-charge long term) aren't affordable for AC. That was probably true for random AC points installed on a shoestring budget to alleviate charging deserts; it shouldn't be true for large-scale deployments of pavement charging in towns.
Although Plug-and-charge provides the technical solution here, there's still the commercial side of things to (potentially) screw up. By default you will have to register your car with every network you want to use before the plug-and-charge will work (plug-and-charge just identifies the car: you need to have a payment method associated with that identity to allow charging to go ahead). Roaming is technically straightforward but history suggests operators often have to be dragged screaming into sensible roaming arrangements.