I almost regret getting rid of my old bike, as I don't think I am getting as much exercise on my new lovely light-weight version. Then I drop a couple of gears whilst braking, and remember the self-rotating seat, crap brakes, etc, and come to my senses.
I think the issue with proper cyclists is that they need to get relevant exercise. If they train on a heavy bike, then they get big powerful legs, which won't be as good mountain climbing as the smaller bloke who has improved his cardio-vascular fitness by training on a lighter bike, and is therefore both fitter in a more relevant way and lighter.
Not applicable for me or any other Joe/Jo publics around, as our income is not going to be affected by crossing the summit a few seconds ahead of someone else.