Geography is largely what stops me, living in Vancouver these days
If I still lived in Shropshire I'd have been all over the Long Mynd ride coming up as that's where I spent most of my time riding retro bikes when they were still new. I borrowed a mate's old Zaskar the other year and still had a hoot.
In general though, it would be the element of competition that would put me off. I know it's only natural, but if people just pish off down (or more likely....up) the trails as fast as they can go all the time, splitting the group up, then what's the point of a group ride? Also, may as well just take a new bike out and go faster
There is a retro 'Show and Shine' every year outside Vancouver, and while other commitments have always got in the way, it's also the competitive element that would put me off going there too. I don't want to take a bike along only for someone to sneer at it because it has a riser bar (because I actually ride the damn thing :shock: ).