A moustache is more than just hair that connects the upper lip to a nose. It is a symbol: a symbol that allows a man who uses it wisely to talk without thinking, and have people listen intently to them. While this clip is old, it is a very good example of this phenomena.
Would the Beastie Boys video above be as awesome as it already if they hadn't worn moustaches? Stroke your 'stache and ponder.
Would the costumes used to portray the Fur Traders be as believable without the use of moustaches? Definitely not.