[gambiting]

Shops have proper authorized terminals, that have authentication keys. The terminal sends the key to the card, then the chip on the card replies with its own details. You cannot read bank cards with commercial NFC readers that you can just buy.

If you manage to get a proper shop terminal(which are only given to proper registered businesses) then yes, you could theoretically skim peoples' cards in a bus or any other public place. The only problem with that is, that you can only charge at most 15 quid, and you cannot get the card details back, so you can't use it for internet payments. And because the bank has your details they can very very quickly track the payments back to you and stop you from stealing money(and not even pay out any money to your account). So yes, the trouble is completely not worth it, which is why probably no one will do that.