Not much waving by me, if the road's heavy traffic.
But mostly try to reply . . . if it's not too late.
Way, way out in the remote country, where you're lucky to see a bike every couple of hours . . . sure, initiating a (minor) wave is polite policy.
But I only get a reply two-thirds of the time.
Where I do give a major & unmissable [geek] wave there, is if I'm riding a pipsqueak trail bike or scooter [scooter is best] and I can see that the rider coming the other way, is on a Harley.
I know I'll never get a wave back [even if I'm likely to be the only other rider he sees that morning or afternoon].
But there is a small glow of satisfaction & amusement, in knowing that he knows my ultra-friendly wave of fellowship is a sign that I regard him as a brother, an equal.