ANPR catches lack of MOT, road tax, and insurance. They also alert on wanted cars.

They are a good thing to have in general, the issue with those things is always data retention and access by authorities. Currently I think that data are retained for 12 months so, for the sake of argument, let's say you commit a serious crime now and only come to the attention of the police in 10 months, well they can still query all of your car's movements at the time of the crime from the ANPR network's database...