I'm pretty far removed from this world of crime and only relay what I read coupled with my biased experiences but I suspect crimes build on top of one another. If you get away with a small crime earlier you'll end up breaking the seal and moving on to higher risk crimes. If you keep on getting away with it you end up taking on more and more risk. At the same time there are not enough resources to enforce a low level crime so fixing the underlying problems is a much better idea.

If you're interested in this topic take a look at When Brute Force Fails (http://www.amazon.com/When-Brute-Force-Fails-Punishment/dp/0...) - I found it a good take on crime in the US.