Yes, sometimes the best you can do without violating everyone's privacy is just the best you can do. You work with it. You lose sometimes, maybe you pay a percent or two extra for insurance to pay out in such cases of fraud, but you accept that it's better than the blatant privacy violation of the other systems.

To put it another way, just because terrorists could use unencrypted email to communicate doesn't mean we have to go and scan everyone's email for threats.