[CULTDIAMONDS]

Any copy should be able to pull anyone over who they suspect of drink/driving - there should be no reason required.
I'm sorry but I've seen what scum drink/drivers do - I lost a relative to somebody who felt "safe to drive home" after a few and ploughed into a bus stop.

Numberplate Boy:
It is a known fact that usually when there is one thing wrong with a car there are also many other things.
Stop a car for illegal number plates and you'll quite often find no insurance, no tax, bald tyres etc.
In your case all they found were the numberplates, in many situations they would have found a lot more.