round here all the council car parks take RingGo so don't need cash for them either (admittedly it does cost an extra 20p)
Our city has just changed to mobile only payments and they charge an extra 25 p 'convenience fee', which I think is a fucking disgrace given that they don't have to go round taking all the money out of the machines, don't lose the money that gets robbed out of them or have to repair them afterwards. And all those 25ps add up to a lot extra if you use the car park regularly.
Given that neither my mobile or the hire car I was in was registered on their system, I decided to not bother paying at all as the free period would have started by the time I had registered my car, phone and entire life history with them and while I was happy to pay 50 p for the parking, illogically, I wasn;'t happy that they wanted 50% extra for the 'convenience' of them not accepting the 50 pence coin I had to pay for parking (it was 20 minutes before the start of the free evening period).
I think I don't see the need to pay on mobiles and cards for small amounts mainly stems from decades of having to carry cash to pay for parking or pay for low value transactions or use small shops, markets, public transport, most independent traders and a lot of other places because you had to and they wouldn't take cards at all or not for under £5/10. It's only the last 2/3 years? where it has become acceptable to pay a quid or two on a card, or that you could use it at all at a street market, or anywhere else 'out in the field'.
Cash still seems more convenient than having to register your mobile here, there and everywhere or for certain transactions, such as work collections, some events and group meals out. If people go to a group meal in a restaurant and they pay by cash, you can easily see what money has been put in, but if people are paying by card, one after the other, I can see that either the last person finds that the amount left is tiny if they are tempted to pinch the tip (this is a common complaint) or else several people have 'forgotten' to pay for their share of the bread, olives, water etc ordered 'for the table' and the remaining bill is loads short and they either have to stump up or try and get the money back from everyone else, who have already paid up in their minds, and have often left the restaurant.