I would assume that with the large number of bikers at such an event, it would be difficult to wave every time you passed another biker. For one thing, you do need to keep your hands on the controls in traffic and while shifting, etc.
This does bring up a related subject, however. I've always acknowledged other riders, no matter what brand or type of 2 wheeler they are on. If my hands are occupied, I nod my head. In my opinion, anyone who rides on 2 wheels is a member of an extended family and deserves recognition. It bothers me when I see certain "bad-ass" types who refuse to acknowledge anyone unless they are riding a Harley, or just think they are to "bad" to acknowledge anyone period. As I stated earlier, I wave at anyone, including the kids on scooters and dirt bikes. We all had to start somewhere - I started out on a 90 cc Bridgestone back in 1966, for instance.