I think you missed the point, it adds a material amount of cost and overhead. Volume matters, particularly where the thing you are charging for is cheap and AC charging is (or should be) a low margin business. That's before considering the much more expensive hardware needed compared to a charger controlled remotely which is almost identical to the one you have on the wall of your house.
Adding contactless payments have a minimum fixed cost per day/week/year plus the usual small % cut taken by the operator, its the former which is important here for a low volume business. So if they only process 1-2 transactions per day that fixed is soaked up by those 1-2 customers. If that machine takes 50 payments a day, that cost is split between 50 customers.
If it costs £1/day (£30/month) just to have the machine switched on, which is a realistic cost which is charged by payment companies to have an active terminal, in the first example, each customer needs to pay 50p. In the second example each customer only needs to pay 1p. The first example is an AC charger, the second example is an arcade machine. My local council will take a contactless payment on a £1 parking charge but the machine serves 100+ people a day, the cost of having a contactless payment option for each customer is 1p.
The thing to consider with arcade machines is that the easier you make it, the more people are likely to spend given its almost entirely impulse driven and the marginal cost of adding a new customer is basically zero. So taking a slightly lower margin could mean you make more money over all and get a better return on your investment. That doesn't really apply to charging which tends to be a distressed purchase (e.g. you buy it because you need it there and then) with low margins and a high marginal cost of adding a new customer.
The summary was that adding contactless payments to slow AC chargers which only see single digit transactions per day will add cost, if you are happy to pay it then fine. But in reality if you ask most people if they would prefer contactless payment and pay 5p/kwh more or save 5p/kwh and pay by an app, most will choose the app. In theory, public will eventually get competitive where there are multiple options to charge and people will naturally gravitate to cheaper chargers.
For another example, just look at the impact the 5p carrier bag charge had literally over night. Buying 5p bags added a negligible amount of money to your weekly supermarket shop but it was more than enough to nearly eliminate carrier bag use overnight.
