I usually honk or wave when someone pulls over and I am able to pass, whether in a car or on a motorcycle. Unfortunately, it's not very often someone does that, but it does happen occasionally.
I think as a society, some of us are becoming very self-centered, and think that everything should revolve around us... it's the Me syndrome, and it's very evident on the roads... I would not be surprised if most of the people who we let by only have one thought on their mind as they pass (it's about friggin time!). But oh well... doing the right thing is doing the right thing, and those of us who know the difference hopefully can pass it on successfully to others.