Motorists generally have always been an accessible target.
You'll find that it pays the DVLA to actively pursue lost revenue by way of clamping release fees etc as it will be self funding, which means that central government does not have to cover the shortfall, whereas Policing only costs money.
Police impartiality, in the UK at least, prevents them from profiting from crime detection and conviction rates. Also unless you want to go down the road of removing everyone from society who inadvertently might have a thought about committing any offence, you are left with having to solve most crimes with hindsight and preventing the occasional ones by way of intelligence gathering... Not so good for victims, but arguably a more reasoned approach than, say, The Minority Report one.