The police believe that if they spot one misdenour they are likely to find others more serious like no insurance and licence. The longer they are around your vehicle finding the small defects the more likely they will find something more serious that the rider/driver may be unaware of. So do those regular checks and make sure you are within the law.
A M&M programme about the police motocyclist showed a rat bike being stoped, it had no rear brake anong other things but a check showed him as a banned rider so it was off to the nick for him.