Maybe you weight sensitive guys are built lean 'n mean yourselves. For me, the fourteen pounds of extra fat I'm carrying over my younger days are a much greater problem. Too much red wine and beer in my early fifties. Still, I'm on the case now. Maybe when I've shed the fat, I'll worry about the three speed SA being a few ounces heavier than a derailleur. I might not feel the need to uprate my brakes either if I wasn't flinging quite so many pounds downhill!!
Seriously though, and racing aside, when you consider the all up weight of a rider and bike, does the odd pound make much difference? If you take my 172 pounds, add it to my Merc at about 27 pounds we come to 199 pounds of fat, muscle, bike and brain.... So how much am I going to notice a 1% weight reduction, and how would that compare with (to put it crudely) taking a dump or emptying my pockets of change before going out on the bike?
Tony