I guess I really never noticed that some teams weren't represented in the set. I am not sure where Stop-n-Go stores were located, but maybe the player choice was somewhat regional? Lots of Hall of Famers, so maybe they were concentrating on the more successful/playoff teams of that time?
Edit - The internet is a great thing! Looks like primarily Texas based...
https://en.wikipedia.org/wiki/Nation...enience_Stores