I'm glad I'm not the only one who doesn't get waves back. I was beginning to think I was doing it wrong.
I bought my first Jeep in 1998 - and brand new, fully stock Wrangler SE (base model with 2.5L 4 cylinder). I waved at every Jeep I saw and got waves back from about 95% of them. Now, I'm driving a fully stock 2013 Wrangler Sport. I wave at every Jeep I see and only get waves back from maybe 75%. Three types that usually do not wave back are women, Sahara's, and hardtops (or any combination of the three).
But, I got into the habit of waving at people in/on similar vehicles when I drove a Bug and when I rode a motorcycle (Granted, I was riding a Honda and never got waves back from Harley riders). Those can be considered "wayalife" vehicles as well. You see a vintage Bug (or any other vintage VeeDub) on the side of the road, you pull over and see if they need help. Same goes for a motorcycle. I currently do not own a VW or motorcycle, but I would still pull over and render assistance. And, I'd do the same thing for someone in a Jeep.