> Stores that sell other age-restricted products.

So far, I've never seen an age verification scratch card sold anywhere

> How would they be traced?

Your ID is collected at retail and its barcode scanned along with a barcode on the card, your personal data and card ID get uploaded to a server operated by the entity that created the cards and/or the state. ID barcode scan can be replaced or used alongside facial recognition, data collected (directly or passively) from your cell phone, your credit card info, etc. Even just being able to link a used card back to the time/place it was purchased could be enough to ID someone and put them at risk.

> It's clearly not important when selling actual poisons so why would it matter for social media?

The main difference is that I can't upload 1 million cigarettes to the internet for anyone of any age to anonymously download and smoke, but I could upload a spreadsheet of 1 million unredeemed scratch off codes to the internet for anyone to use. It seems highly likely that codes would get sold, shared online, generated, or leaked which means cards would be ineffective at keeping children from using them.

Why should we be okay with jumping through a bunch of hoops that don't even do what they're supposed to in the first place while costing us money and opening ourselves up to new risks in the process? I reject the premise that proving my identity to a website is necessary let alone being worth the costs/risks. Scratch cards seem likely to fail at being private or effective. Of course, "Think of the children" is really only the excuse. Surveillance and control is the real motivation and any system that doesn't meet that goal is doomed to be replaced by one that does.