If I had SAG or raced I would care a lot about weight and aero.
Who cares if you bike weights less than 15 lbs if you carry 5+ lbs tools/tubes/food/water. Then another 5lbs of clothes/shoes/money.
To go from 20lb bike to 15lb bike is probably 5k (WAG).
I must admit there a few 3 to 5+ miles hills that I wanted to try and go up with only my bike/shirt/shorts/shoes ( no tools/water/tube/food/lights/helmet/etc.. )
As for myself I lost 1 to 2 inches off my waist and probably could use another 1 to 2 inches.