Then there are those of us who actually race, and train with power and know how hard it is to add 5W to our threshold power so giving those up on the bike due to rolling resistance, aero, or weight when the guy you're trying to stay with in the group has considered the same thing. The engine is the most important aspect but you can put yourself at a disadvantage that training can't always overcome. Gotta remember those in your Cat are likely training just as much if not more than you or have the genetic gifts to be able to hang. Its not like when you're out on a group ride with a bunch of randoms of varying fitness