These checkpoints are purely to stop motorcyclists. Not cars. I was stopped last year. I was completely legal, going below the speed limit and was pulled over to have my bike and documents checked. The reason the police officer said when I asked him, was that dead motorcyclists cost too much money to clean up.
And if there is anything wrong, then of course you get a fine to swell the coffers of the government. And 3 points on your licence.
anything for the government to make a buck right...