Just a story of one, but here goes:

Back in the 90's, my parents were making a purchase with a card, and the cashier told them that the machine was down, so he had to take a copy of the card to run it later. A quick swipe of their card throughv something that impressed it on carbon paper and off they went.

Not long after, police showed up at their door informing them that said cashier's apartment had been raided and a whole stack of copies of cards had been found; for every one he made for the store he kept one for himself.

Mind you, this was before ubiquitous cell phones, internet access, and way before chips in cards for encryption. Whether a similar tactic could work now I have no idea.

Back in the 90s when our family went on a big vacation abroad we were always advised to never agree to have our card carbon copied for exactly that reason. Though I think there was one gas station where we had to, because we were out of cash. (Back then ATMs were new, and POS was only for the rich foreigners. Strange that nowadays we run around with everything RFID/NFC and multiple cards. And yeah, this was before smart phones. Those were simpler times :) )

Add or inflate the tip, then cash out.

Customer A has an open tab, customer B pays with cash, put B's drink on A's tab and pocket the cash.

Ah, yeah, that happens with or without customer B unfortunately. (And of course drunk people are easier to trick with cards, but then they are easy to simply rob of cash too.)