They don’t. It means the transaction is rung up, the woman behind the counter takes her card, types in all the information, swipes the card, then presses cancel instead of enter. The charge never hits the card but the cardholder doesn’t know it because it seems like the normal process
this whole idea is why most places where I live make you use the chip on the card if you have it. There isn't much you can do since the transaction has to be confirmed twice (thrice with a signature sometimes) by the buyer.
Although the manager or owner, if running the register at the time can just fucking give you whatever for free and circumvent it... which is always appreciated by me when it happens :)
My store is the same way, and the register always prints two receipts for card transactions, one that 99% of customers will need to sign (even for debit cards if it has a chip) and a customer copy.
I worked with someone once that would charge people for coffee, take their money but not ring in the sale then pocket the money at the end of their shift. I've seen some scum moves.
Although the manager or owner, if running the register at the time can just fucking give you whatever for free and circumvent it... which is always appreciated by me when it happens :)