I have to agree that a lot of people do it.
However when an officer in a marked car does it, it sends a clear message. " Look at me, I don't know the rules of the road, but here I am trying to enforce them." Problem is if the officer doesn't carte, or worse realize they are breaking the law, then that make them incompetent. How incompetent is that officer? Should that person be an officer? How safe can an incompetent or stupid person make our streets? See the chain of thought here?