I think waving is required when you own a Jeep.
I don't wave when towing basically because no one is looking to be able to see it. As I drive my eyes are always moving front, sides, mirrors etc. I generally only have one hand on the wheel, just habit.
When we travel we see every other camper and usually yell out, an Outback, a Jayco, a big rolling turd, whatever it is. I always look over to check it out. When someone is passing me I also say here comes a whatever it is. When they pass I always check out the tow vehicle, the trailer and the hitch if I can. Every time, no matter which direction, the people in the other vehicle are eyes forward, holding onto the wheel and not enjoying the ride. For me, the ride is one of the best parts of the adventure.
If you wave, I will wave back as I will see you.