I am just about old enough to remember this time - it’s funny to think that security hinged on checking if the signature looked ‘right’. For cheques I remember here at least for yours to actually be accepted anywhere you needed a ‘cheque guarantee card’ which was basically just a debit card but with a fancy hologram - so a certificate of your ‘goodness’ - up to a certain limit per cheque. The shop would copy the details and this would supposedly guarantee they’ll be paid.
I was going to say that shops could have asked for ID - but at this time driving licences didn’t have a picture and weren’t cards - so no one carried them anyway. There was probably a lot of ‘subjective’ acceptance around the place (‘does this person look trustworthy, would they really be given a credit card or did they steal it?’) come to think of it…
And before everything was networked, there was no way for a store to check with the credit card company that the card wasn't reported stolen. That's the trusting people part, it's the store that is trusting people without the ability to even verify that the card hasn't been reported stolen.
Yes, there is a paper trail, but the situation I'm talking about is analogous to a bad check or a counterfeit bill -- there's no recourse if the bad actor can't be found and the store is on the hook.