Actually, I think you left something out - or perhaps you need to specify which state you're in. Where I live, the law says keep right except to pass or turn left. So, what if you are in the process of passing? If you expect the person who is passing to pull over, then that means all the cars behind that person, up to the last one, also need to move over, doesn't it? If the driver who is passing were to slow down to get behind the car, it could be dangerous with someone close behind, who will probably think he's playing games by slowing down, and go postal.

Personally, I will speed up to get around the car to my right, if I don't have to go too far above the limit. I once got a ticket for doing something similar to this, when a cop on the other side of the freeway saw me, did a U-turn and stopped me even though I was no longer speeding. He said I probably slowed down when I saw him (I never saw him), and since it was about 400 miles away from my home, taking off work and driving up there to try to fight the ticket wasn't really an option.