I did a few "wave back" experiments this weekend.
My girlfriend and I went out to the Delaware Water Gap area. On our rides, we're almost always in full gear, from motorcycle specific boots, to pants, jacket, gloves, etc... The bike also had saddle bags.
When we were in full gear, not once did I get a wave back from a cruiser driver.
We took a trip out to Hawk's Nest (saw a few Bandits on the road, all waved back), in jeans. Still no waves from the cruiser set. Sport bikes and standards almost always waved back.
At one point, we were heading to the supermarket on a stretch of road that is straight for about 5 miles. We were both hot in our jackets, so we put them in the saddle bags. To my surprise, almost every cruiser rider waved back at us.
Is it the gear that keeps them from waving?
Probably 100 waves went unanswered.