As for specifically REs, people buy them, then don't have the patience to break them in, or they shake too much, or just don't like the old Brit thumper feel, or the perceived lack of power, or other reasons mentioned above. The same goes for 250 Hondas. Personally I think one would be a great little bike, but people buying bikes have a different perception of what they then it will do and what the real world is. A lot of it as much to do with media hype, aka BS, as anything. When I was riding liter bikes the specs and media would have the 600s going as fast as the liter bikes and easier to handle. But in the real world, the guy with the 600 would have to flog the hell out of it to stay up with a liter bike. He might be able to stay with it, but he'd use a lot more gas doing it!
Kinda like the dude saying he could outrun an Enfield with his 250 Pigaggio scooter. Bring it on, bud!
Bare