Um, it's called "moving with the flow of traffic". And cops know where the 55 mph limit is too low and traffic flows at 5-8 mph over. They can always go there to meet their quota er, keep their "activity" up.
It is a great way to undermine respect for the law and peace officers er, "Law Enforcement" officers.
Up in the Chicago area on I-90 etc. traffic moves at 80 mph and cops whiz right by you (unless they are looking for someone to pull over)
Having a high end Volvo pass you at 100 mph+ happened all the time and I never saw one pulled over.
Of course though we could drive like that in conditions that would shut down the entire state of Texas. and I am from Texas.