It's not an effective deterrent because people who commit crimes don't often stop and think "oh if I do this I will get caught." In fact if you've ever reported

It's not an effective deterrent because people who commit crimes don't often stop and think "oh if I do this I will get caught." In fact if you've ever reported crimes to police as a victim you've probably had the experience that there's really not much that they do other than take a police report and if it's a crime against property basically tell you to call your insurance company. Prison is a deterrent to you or me because we think things through before we act. But criminals often have really bad impulse control relative to the general population and so any preventative measures that rely on impulse control won't work on them.