Questions of the Expressway

DocBrain has discovered new rules of the road. Here is what they are:

1. DocBrain drives expressways with his cruise control on. If I am going just a few mph faster than the car in front of me, when I try to pass, the other driver will speed up making it harder to pass. Once I get past the other car, it immediately slows down. If you are one of those drivers, why do you speed up?
2. Sometimes, when the other car speeds up to exactly equal my speed, I slow down and pull in behind them. I then reactivate my cruise control and, voila, within 30 seconds I am right on their rear bumper. When I pull out to pass that time, they let me. Why?
3. As I said above, I drive on expressways with my cruise control on. When a driver gets on my bumper, I do not go any faster or slower, but it sure is annoying. If you are one of those drivers who gets on other drivers rear bumpers, what do you hope will happen and how often it works for you?
4. Rules 1 and 3 get into conflict when I try to pass a slower car. I am not the fastest driver on the road, so I pull out to pass, the car I am trying to pass speeds up, and cars behind me catch up and get on my bumper. As I travel about 5 mph above the speed limit, I do not have much leeway to speed up and yet do not want to slow down. What is the solution to this problem?