I have read on different forums and other online places that roadies typically don't wave to other cyclists. Either because they're snobs or just training too intensely.
I am primarily a roadie. It is true that I can be a bit of a snob and I definitely ride/train hard. However, I must note that I make it a point to wave to every cyclist, jogger, walker etc... that I happen upon. I'm one friendly M****F*****!
Typically the roadies I encounter wave back. Maybe because we acknowledge our own kind. You know who doesn't wave back? Recreational cyclists and newbs w/o helmets, that's who!
Oh, and commuters. I commute regularly and I encounter a lot of salty, angry looking dudes with their bikes loaded up on a dialy basis. Maybe they would rather be at work...😕
Anyway, I think waving is cool. It's the right thing to do. Just a nod and tip of the hand to say "Hello there fellow cyclist - Rock On!"