To guys who always complain that girls are spending too much money on saloon to do their hair

Why does head hair grow to great length whereas body hair doesn't? Nobody knows exactly, but some anthropologists believe the purpose of long head hair is to give you something to tie ribbons in. No kidding. Quoth one, "the functional significance of long head hair is almost certainly adornment, providing for the 'sexual selection' that Darwin correctly argued was a potent factor in the evolutionary process." In other words, when you drop sixty bucks at the beauty parlor, don't feel guilty--you're helping to advance the species. [1]

Reference:
The Straight Dope, Cecil Adams