The classic principle of Anglosphere common law is that its better to let 10 criminals get away with it than to convict 1 innocent person. The same idea applies to fraud because overzealous fraud prevention causes problems for legitimate users whose actions incorrectly get detected as possible fraud. The benefit to tolerating a low amount of fraud is that your product won't be hostile to your legitimate users. The benefit to tolerating a low amount of crime is that you will live in a free society rather than a dystopian tyranny. Freedom is good and it is worth giving up quite a bit of safety for the sake of being free.