For most riders (included racers, it seems) most climbing time is not done standing - on the way up weight is not your friend climbing for the vast majority of people the vast majority of the time.
Similarly, very few people are doing hour long climbs as a high percentage of their riding and will never be able to lose 10% of their total weight very often! A lot of bike weight savings are in the 1-2% of total bike+rider weight, or lower.
Using bikecalculator.com, for my weight (220) on a 60 mile ride with a 1% overall average grade (about 3000 ft of climbing) at an overall average of about 16mph works out to be a 3:44 ride. If I drop 20 lbs, that time goes down to 3:38 - I saved 6 minutes in an almost 4 hour ride. Very meaningful in a race, not very meaningful outside of a race.
From that point, taking 2 lbs off my bike saves about 30 seconds.