If you expect to be caught for committing a crime then it is a deterrent. But that is hard to maintain, and once you hit a tipping point and it’s out of control, it is much harder to get it back under control. Then it’s a question of is the juice worth the squeeze? Because you need to squeeze hard. If you have no reason to commit a crime that is the better way to go (eliminate poverty, inequities), but way more complex and and way more political. It’s easy for people to say just add police.