1) It is not a speed trap if the speed limit is posted and you are caught exceeding it. It is called enforcement.
2) Increased enforcement is a byproduct of the war on drugs. You stop lots of people and write tickets. Then when you care to stop a suspicious vehicle to check out the occupants for drugs the numbers will prove you did not stop the person because you were suspicious of them running drugs in the car as they went by (which is an illegal search usually unless the officer has more than a suspicion ) BUT you can stop them for a traffic infraction (real or made up) and if you gather further evidence during the stop then an arrest may be made.
The above has been the subject of numerous news stories on I10 in Louisiana and Texas
Again there is a distinction between a speed trap and strict enforcement.