Police enforcement of speed limits varies greatly by regions / states. Im sure a lot has to do with how reasonable or unreasonable the posted limits are. In the blue states of the northeast (where the people who are involved with setting speed limits think they know whats best for you) the posted limits are generally about 10 mph below what the AVERAGE driver goes. Instead of setting the limit at that average speed and enforcing it, they continue setting the limits artificially low and only arbitrarily enforcing it at 10 or 15, or whatever the LEO feels like that day, over the limit.
Their argument is that if they were to raise the limit by 10 mph the average driver will then drive 10 over the new limit. Only problem with that argument is that it has been proven to be false. For example, on I-93 in New Hampshire the speed limit is 65 mph from the southern border as far north as Concord. North of Concord it mysteriously goes up to 70 mph. The average driver seems to go along at about the same speed in both sections, which is about 70 to 75 mph.
Concurrently, the nearly identical interstate running northwest from Concord up to White River Junction VT is still posted at 65 and people drive that at 70 to 75 mph also. Very few vehicles, including loaded semis, drive at the 65 mph limit. Ocassionally I will set the cruise control on my pickup truck at 65 mph and just stay in the right lane. All of the traffic will come up on my tail and pass around me as if I were going 10 mph below the speed limit.
The worst part of all of these capricious speed limit shenanigans is that it has trained the average driver to be an intentional law breaker. It has instilled a pervasive negative attitude in the public perception of police, particularly the speed enforcers. They all know that they are breaking the law and trying to get away with it, as is evidenced by the flurry of brake lights whenever they see a patrol car in the median, or on the side of the road. So, if speeding is OK, what other laws become fair game for disregarding since they shouldnt really apply to you?
And to bring this back around to the topic, all of this is why I feel a need to use a radar detector on my bikes. I generally ride at near the average speed of traffic, around 75 mph on the interstate for example. But that speed is 10 mph over posted in most cases. If a LEO arbitrarily wants to stop that shiny red motorcycle for 10 over he can. I am convinced that the some (many) of the police in this area will pull a motorcycle over any time they can. But, if I know hes out there before he gets a speed from me, I get to continue along my way unmolested.