The English used bows, not because they were killing machines, but because it's what they had. Fighting i.e. France, which was far larger and wealthier, they would always be outnumbered, but bows could equip a much larger segment of society than could the arms of the knight, thus bringing about some kind of balance. As a missile weapon, the bow synergized well with defensive tactics, forcing the enemy to advance and thus giving time for the terrain to disrupt their formation. The bow's ability to gall horses neutralized one of the best ways to counter the disordering effects of terrain on advancing formations. They also forced armored men to advance with visors down, resulting in their breath becoming stale and leading to fatigue that made them easier to kill with weapons besides the bow. Ultimately, though, the bow falls victim to the zeroth law of pre-gunpowder missile weapons: man has the muscle power to carry defensive arms that missiles propelled by human muscle power cannot penetrate.