Being an archer is popular. If there is a too large percentage of archers on the server the gameplay becomes shit, and people become archers to counter archers. Archery's popularity exceeds the the amount of archers the balance can handle. So to weed out a lot of the not so hardcore archers, they make the class individually underpowered, to prevent the class as a whole to be overpowered.
So if you all stop desiring to be an archer so desperately, the individual archer can be buffed.