Who says it would need to be so strictly enforced? Do we hire police officers to peep in each window every day to ensure we're not trafficking narcotics from our home? In principle, if a narcotrafficker keeps a low profile, the police would never know. The same would apply to fornication laws. Just don't have sex with anyone who might falsely accuse you of rape, don't repond to a sex ad online, don't have sex in a public park, don't film it and post it online, don't brag about it, and no one should know, right?
Why would we police fornication any more than we would narcotrafficking? If we don't spy in people's windows to catch would-be murderers, why would we spy for this?