Interesting. In Australia you can charge a surcharge, but only what the interchange fee cost you. So airlines especially used to charge large fees, like $12 or something, and now can only charge a few dollars.
Before this law in the UK it was mostly small businesses (e.g. local independent grocery stores) charging 50p per transaction. I think the law was probably to encourage uptake of contactless payments which are targeted at these small transactions.
It's still legal here to have a minimum transaction value for paying with card, which some businesses use. But since the pandemic it's become more common to find businesses that don't accept cash than the other way around.
I occasionally had disagreements with shop owners because I didn't have cash and I wanted them to add the payment fee manually so I could pay by card and actually - you know - buy stuff.
A lot simply wouldn't - like I was attempting fraud or something.
I once tried to buy a beer in a small corner shop. The beer was 2€. The minimum charge for card payments was 5€. I agreed to pay 5€. The shopkeeper refused to charge me 5€.
I walked out without my beer, sad, and wishing I'd remembered to carry some cash that day.
It's still legal here to have a minimum transaction value for paying with card, which some businesses use. But since the pandemic it's become more common to find businesses that don't accept cash than the other way around.