Why did they stop making Root Beer Kool Aid?

It was extremely popular in the 50s and 60s in Lincoln, Nebraska. I helped in my aunt's grocery store. We would get one carton of all the non-root beer flavors and one carton of just root beer. The root beer was always sold out long before all the other flavors began to even look like we were selling any of them. Hard to imagine how it came to be unpopular. I still make my own (uncarbonated) from the concentrate.