Why is weight so important?

[mrnoble]

This will be our fourth build season, but I've only been utilizing chief delphi and other resources over the last several months. I'm curious about something that seems to come up frequently in technical discussions: weight. Why are there so many individuals and/or teams concerned with having the minimum weight on their robot and parts (some recent threads on wheels that weigh less than a 10th of a pound would be a case in point)? Of course, I understand the need to remain under the limits (our bot had to be drilled at the last minute to make the weight requirements last year), but really, once you're under a certain maximum, what's the point? Is it just something to add to the challenge from an engineering perspective? Is it bragging rights? Are their special awards/categories that I'm unaware of in my ignorance of FIRST culture? I appreciate any enlightenment you are willing to bestow.