Not a law of nature, but there are laws of man against “Tipping-off” [1].

Add in the fact there are people trying very hard all the time to defraud the payment processor.

So now you can directly measure false negatives in fraud detection, but your false positive rate is harder to figure out. And whatever mechanism you use to recover from false positives can be abused by true fraudsters.

So it becomes a hard problem - but it is a problem which customers of the payment processor are paying them to solve. So it’s definitely reasonable to expect better.

1: I think a reasonable-ish definition of tipping off: https://onlinelibrary.wiley.com/doi/10.1002/9780470685280.ch...