A herder would use it to direct the flock - herding dogs are a very recent innovation.
They would also use it to hunt their dinner and defend the flock.
So a multi-use tool.
In mexico it's used as a bird scarer and also to hunt them for food.
In the uk, mainly used for throwing tennis balls for dogs.
I've often used mine as a dog lead, when I've either forgotten to throw one in the car or found a stray dog.
My friend Puchi, grew up in tibet on the family 'farm'. She used her sling to herd the yaks. She also uses the longest sling for target shooting I've yet seen. And a singular technique.
That is her target sling.