Originally Posted by Fiery

My guess is that it's a combination of being unaware that Campagnolo pads exist for Shimano-style holders and the general tendency to look for non-groupset manufacturers when buying aftermarket pads. Add to that the image of prestige, style, history of Campagnolo, and people just don't think "I should get me some Campagnolo braking pads for carbon wheels" unless they actually have a Campagnolo groupset and/or Campagnolo carbon wheels.