The shoplifting metaphor might be simple and relatable, but it's inaccurate because it's not just someone stealing in your store, it's other people putting stolen merchandise in your store to be re-stolen by someone else.
The real metaphor is, "If you own a pawn shop and let obviously dirt broke people come in and sell you stolen Rolexes all the time, you may be shut down."
No, that's not it either. It's not that your letting people do stuff you know they can't legally be doing. It's that your pawn shop is so incredibly huge that you can't be sure what's happening everywhere at any given time. By the time you get to one side to see what's happened, the other side has turned into Somalia. You put up signs, hire security guards but the floor space is so enormous it would be prohibitively expensive to keep any wrong doers out and trying to do so would cost more than the whole thing is making in revenue.
It's not that mine is incorrect. It's that we're both correct, plus a whole other slew of equally plausible scenarios. In plenty of cases it is what I described, plus the owner is painfully aware that his shoppers mostly only buy from the fake watch guys, and they hide behind a description like the one you've crafted, crying "poor me, my job is so hard."