If I recall the credit card agreement - it’s been a while - the credit card company, not the merchant, assumed losses provided: The merchant was sure the card was present (swipe, imprint); the signature matched (pretty arbitrary and hard to prove); and the card was not reported stolen. For that last bit - remember back in the 80’s they were checking big books of CC numbers for the card? Then dial up swipe readers (and later the internet) would validate the card.
Many merchants had a limit - say, $50 or $100 depending on the business. In the “Good Old Days” they had to phone and get an authorization if the purchase was over that limit. Then the dial up/online devices automatically got the authorization code. This verified the card was within the credit limit and not reported stolen.
If the authorization was OK, or the card was below their “verify” limit and card and signature matched, the merchant was not on the hook for the purchase. A card imprint or swipe proved the card (or an imitation) was present. The client’s signature on the receipt proved he had authorized it. Unless the credit card company suspected hanky-panky (ringing things through double, that sort) the merchant would not lose. That is why additional ID was not necessary according to the CC company.
That was the major appeal of credit cards. Unlike cheques, there was not supposed to be serious risk to the merchant. A proper credit card charge was like money in the bank.
(Of course, online or mail orders were a whole different ball game).
There’s an interesting movie about the guys who developed an online credit card charging system, and how porn sites and crooks combined to try to take the credit card companies to the cleaners using that system. At one point, one consortium of porn websites was, IIRC, responsible for 20% of all credit card reversals in the USA. After that, credit card companies instituted new rules, if your reversed transactions went over X% they would fine you 10% of your total credit card revenue.