You would think that it would be helpful to leave Backpage alone, because the cops could use it to figure out who the child sex traffickers are.
It was far more useful as a honeypot & revenue generator for them through John stings. Setting up a fake Backpage ad for a weekend and raking in $20k through the relatively safe act of fooling non-violent offenders is the best deal out there for police.
At the end of it all you get a nice feel-good headline about how the local PD arrested 40 sex offenders.