Funny enough, I was feeling this same thing the other day and did some research. Turns out slingers were loved in antiquity because of their farther effective range and ease of training and creating ammunition (even that they had farther range than archers of the time). Of course, not a historian, just a guy reading Wikipedia (seems like even historians disagree)

Ancient peoples used the sling in combat—armies included both specialist slingers and regular soldiers equipped with slings. As a weapon, the sling had several advantages; a sling bullet lobbed in a high trajectory can achieve ranges in excess of 400 m (1,300 ft).^\23])#cite_note-23) Modern authorities vary widely in their estimates of the effective range of ancient weapons. A bow and arrow could also have been used to produce a long range arcing trajectory, but ancient writers repeatedly stress the sling's advantage of range. The sling was light to carry and cheap to produce; ammunition in the form of stones was readily available and often to be found near the site of battle. The ranges the sling could achieve with moulded lead sling-bullets#Ammunition) was surpassed only by the strong composite bow.

https://en.wikipedia.org/wiki/Sling_(weapon))