You cannot attack with a broken weapon, the same as you cannot shot without projectiles, so you need to repair it or find a replacement, the same as finding more projectiles or crafting more. If you do not fulfil this requirement you cannot attack the way you want, so it is related. Both can be annoying in the long run IMHO because we are not talking about spells, healing or shapeshifting or supernatural abilities, we are talking about basic attacks... for a warrior that seldom has other ways of intervening in the combat.
If we are talking BG-BG2 I think it was a handicap to have stacks of only 20 arrows like in the original game. Thankfully that was fixed.
