It generates more money. The kits don't cost as much. They are more aerodynamic. They are less able to be spotted by ANYONE, not just speeders.

Imagine any car possibly being a "cop".

Sure MARKED presence work for about 2 miles (1 before and 1 after) of where it is.

Evidence average speeds 82MPH before a median sitter, 68MPH within view of the sitter, 87MPH after the sitter is out of view. Speed limit is 70MPH. This was on I75 north.

After the overpass shooters and collectors on I96, it was nearly 10 miles before the average went up past 75MPH.

So, you tell me.