Cannondale know how much their frames weigh, but there is a fair bit of variation (hand layups), then they paint them, more variation. (white paint weighs more for example)
Then they sell them to annoying people who strip the bike down to it’s component parts and then moan about the frame not meeting the nominal weight that the manufacturer might have given. (Or the quoted minimum weight for a small frame with no paint, Colnago, i’m looking at you)
Or they moan that it’s 200 grams lighter than the (top limit) weight quoted, so it must be weaker and more fragile.
Just easier to not say anything.
Someone on the net will have stripped one down and complained about the weight, just google it.
This +1, although I suspect variations are smaller than that. Things like pre-preg carbon cloth will be very accurately made and cut, and part of QC will be to weigh the frames so they can tell if a sheet’s been left out.
Essentially it boils down to:
1) You care so much about weight that you’ll buy the lightest regardless, so what’s the point in them telling you as 9/10 times you’ll know of something lighter. if they don’t tell you they’ve a chance you’ll convince yourself you’re actually number 2 below.
2) You don’t care about the weight and happy to accept that a well designed bike rides well regardless of weight.