Because the urge to just have results tends to lead to scapegoating someone and locking them up without actually addressing any of the root causes of crime, IE the cases where people fall through the cracks of society and have no route to stability except by committing crime.

To truly wage war on crime you need to wage war on desperation, something that is nigh impossible to do for most conservatives who just want to solve the problem by building more jails to throw away any hooligans being too noisy.