@Kovacius @Najaknevrec Thanks for clearing that up. I thought arrows and bolts were a little more effective than that. I guess I was wrong.
Arrows and bolts were effective against the majority of the lightly armored (if at all) masses of peasantry, and reasonably effective against the moderately armored regulars. It was of limited usefulness against the massively armored knights, who were essentially the "tanks" of their day, and represented a small proportion of most armies. Even then, an arrow or crossbow bolt could still inflict crippling injury, especially at shorter ranges, although typically not a fatal one. On horse, the Knight was vulnerable to having his mount shot out from under him; on foot, his mobility and vision were severely restricted, and he became vulnerable to being outflanked and encircled. First, a Backplate is not as strong as a briastplate; second, those archers also typically carried daggers, and many of the previously injured Knights suddenly became prey to gangs of the lighter troops.
The main advantage of crossbows over bows was that it took a high degree of skill and constant training to hit targets with a bow. Any conscript could point a crossbow in the right general direction and pull the release, which suddenly placed lethal power in the hands of the average peasant. The threat to the social order was far more serious than the actual military effectiveness of the weapon.
One "problem" with MW's crossbows was that they always did rated damage, even if you didn't take sufficient time to rearm them. You could "spam" bolts at an absurd rate. In actuality, the reload time is considerably more than that of a conventional bow.