I read at one point--I don't have a cite to back this up--that the primary reason the bow & arrow became the primary ranged weapon of choice for mass combat over the sling had nothing to do with it being more damaging, or a greater range, or any of that. And it sure as hell wasn't for economic reasons; you can find rocks anywhere, slings are cheap to make and maintain, bad weather doesn't do them in like it can bowstrings...

No, it was that slings were so much harder to achieve reasonable competence in compared to bows that it was just easier to get the expensive, fragile, requires-constant-ammunition-making weapons and train thousands of people to use them quickly than the other way around.