> I'm sure there's a fraud angle where someone signs up with a cheap prepaid card, runs up a huge bill, and then the business has no recourse. Though I'm not familiar with Lambda Labs or their billing.

I work at Lambda Labs. This is basically the reason. Fraud has been a problem and these are attempts at us granting resources only to legitimate accounts. We have struggled with people spinning up resources and not paying for them, which is detrimental to our business.