Google doesn't sell the cards directly - at least not the ones purchased at the supermarket and used for scamming. There's a scummy industry of middlemen that handles this - that's why every store can sell basically every gift card; they don't have their PoS interact with every single vendor's API, they delegate to a middleman. So Google gets very limited data at purchase time, and is not technically the merchant selling the goods in this case.
> doesn't google have the responsibility to ask the giftcard user where they got that redeem code from
What will that change in practice? They have 2 options: either accept any answer, and nothing changes, or decline some answers, meaning either legitimate usage gets disrupted or the sites laundering the cards will just tell you the "right" answers to say.
> At least warn them several times, and then cut those buyers too?
Most buyers are one-time users; it's a relatively niche market. Mostly teens/etc who don't have their own payment card or are willing to go through the whole hassle for a small discount. As per the above, cutting people off would likely hinder legitimate usage.
Ideally the whole "gift card" industry just goes away as there's no good reason to have it when we already have the ultimate form of "gift card" in the form of money... but until then, even if Google were to step out of the game someone else will step in (the company issuing the cards isn't directly involved, their gift card is just used as a negotiable instrument in lieu of cash during the scam transaction, so any company's will do).
> has skin in the Cambodian scams
Cambodia/etc is pig butchering/fake investment scams. Gift cards and redeeming is exclusively Indians targeting the US market (in the UK they have money mules to launder actual bank transfers, so no need for gift cards).