Kitboga has shown in his videos where a victim will be at the store, and will either see a sign that warns about gift card scams, or is specifically told by the cashier, and still buys them.
Why? Because often the scammer already has remote access to their computer and has threatened to lock it permanently, or take over their bank account, or whatever else. Maybe they’ve already used the infamous Inspect Element to ‘zero’ their bank account. Scam or not, the victim believes that they’ve already lost.
You would need a cashier to have, essentially, Kitboga-level knowledge of current scams so they could accurately explain why the victim shouldn’t buy the cards, explain that their bank account is actually safe, and also ideally provide instructions on how to the scammer off their computer. That probably goes beyond the scope of most cashiers.