The big problems are this:
1: The "It is legal so long as I do not get caught" mentality of many drivers (story follows) and
2: Government budget cut backs have greatly reduced police presence.
Story:
Some years ago the Michigan State Police parked either a plane or helicopter over a segment of I-696 international speedway.. er, Freeway early one week. Before the aircraft had to return to base for re-fueling they wrote 85 tickets, Slowest they wrote wasw 85, fastest 105.
A couple days later they parked the other kind of aircraft in the same place.
Another 85 tickets, once again you had to be going 85 to get an invite to visit with a judge, and the winner was doing 105.. Why do I think it was the same guy both times?
Only thing that stops them is a cement wall.