I think that people might pay for the convenience of getting a bag full of proper chickpeas with no duds and no stones (I've heard of this, but never really seen it).
Maybe some day Suraj and NuPak will go a little further with their cleaning and get rid of damaged beans and not just stones.
Though, frankly I think they could do better than average with a specific gravity/densimetric sorter; it would probably require fewer passes through the optical sorter as well.
The equipment costs money; and reduces the volume of "product" left for sale. Your problem is capitalism - the companies don't do that because it lowers their profit.