IMO a durable (steel preferably) sub 24lb bike is ideal for anything but racing. Less expensive, less to worry about, significantly harder to break. On the other hand a lot of people that have money to blow and want nice things will end up buying light racing style bikes even though they don't race, and there's nothing wrong with that although I don't think anyone would say it's necessary. Part of the problem too is people with cheaper / heavier bikes being jealous of people that have nicer bikes and over-blowing the issue.

I guess to summarize my thoughts, I think casual riders overestimate the importance of the bike they're riding.