Earlier quoted context omitted.
That's not even universally true, though. I've been to bars where they scan the barcode on my drivers' license. I assume that's more convenient than reading the data off it, so maybe they're just doing it for convenience and aren't storing the data anywhere, but who knows, maybe they are. Maybe there's a database somewhere with a list of name, date, time, location tuples for some of my bar visits from years ago. Cree…
Yeah, grocery stores swipe ids too. Thankfully I’m too old, they don’t ask. Have to teach kids to not allow it. Definitely stored.
Not well-designed ones. I think you overestimate how much retailers want to even possess sensitive information like that.
What's going to be stored is the fact that an of-age ID was scanned, and possibly the DOB. This is to protect honest cashiers and to have a way to punish ones who might sell to the underage. If an underage sale is reported, they check the audit log and it says the transaction had an ID scanned the cashier can be cleared of wrongdoing. Unless it's the same DOB always being scanned, which seems like some kind of dishonesty.
I do not buy that the supermarket chain wants to use your ID card data for any purpose. First of all, they don't need to, they have (most people's) loyalty cards that do a much better job as they're swiped or entered even without buying any beer. Second, again, only downsides come from saving it. If they were to sell the data and be caught, terrible. If they were to get hacked, terrible.