The problem (as I see it) stems from the public perception of policing. The media (and politicians, and police to some extent) make a big deal about low occurance crimes, demanding that the police do more to prevent crime. In our society we love to have league tables and see which force is arresting the most bad people (which is what we pay them for), so statistical collections were inevitable.

The problem with it is, as you say, the police can hammer the stats with lots of low impact but high occurance offence arrests. The public see that Force X have made a zillion arrests so their police must be doing something right… (Any readers from the North East?).

A force which spent time and effort on crime prevention would eventually lose out in the budgets, less arrests means the force must need less money…

Crazy system but as far as I can see, unsolvable.