I agree that differences in bike weight make very little difference in speed in the real world, that the difference in speed objectively matters not at all to non-racers, and very little to non-pro racers. I agree that other factors (esp. rider position and other aero considerations, and rider weight) have a much greater effect on speed than bike weight over the course of a real ride.
However, a lighter bike can feel faster, even if it isn't really faster, or only marginally faster. That can have some value, the magnitude of which is defined by the buyer/user (and can even be a negative value - some people prefer a "solid/slow" feel to a "racy/twitchy" feel).