What users don't see is that a single good actor will make, at most, a dozen such claims in their life, while a malicious one might literally make hundreds of t

What users don't see is that a single good actor will make, at most, a dozen such claims in their life, while a malicious one might literally make hundreds of them a day. The scales are different, by orders of magnitude. It's not unimaginable that just 0.001% of your users (in terms of actual humans / entities physically using your service) are fraudsters, but 99% of your signup or login attempts / interactions with your service / "I'm not a fraudster, pinky swear" support claims are fraudulent.