Chargebacks. So the idea is that the unethical agent buys the keys (either themselves or with a stolen card), sells them to a key reseller, and then initiates a chargeback to get their money back (either for themselves, or the person who had their card stolen does it to understandably get back the money stolen from them from the illegal purchase).

Suddenly, keys were "generated" for money that no longer exists. The key hopefully gets deactivated at this point, but then someone buys one of those keys and it doesn't work. Support calls and angry customers ensue.