This is a motorcycle thing, this waving at every single person who's using the same type of vehicle, regardless of whether you know them from Adam. People driving cars don't do it. People driving trucks don't do it. People driving tractors or backhoes or bulldozers don't do it. People on rollerskates don't do it. People on foot don't do it. People on horses don't do it. Aaaaaand...people on bicycles don't do it.