That's a pain. I lived in Cornwall for a couple of decades, and did lots of work on hookups at sites, and back then site owners were really keen to get as many hookup points in, and keep them working, as they could, as everyone wanted them. I guess things have changed with the rising price of electricity. Pity, as most of the sites I worked on had the full 16 A available at each outlet.
We now only stay at places that have charge points, have done for years. Some make a small charge for using them (usually about a fiver) some are free. Not yet come across any that accept payment cards, though.
You're right, I think it's mostly about selling their wine and cider, but the cafe is definitely a step above the typical sort of places where chargers are located. Every time we've stopped there we've also found a charger free, too, perhaps not than many people are prepared to drive a few minutes off the main road for somewhere to stop and charge.