Uhm...because we are uber fans?
Look, I'm not saying that all A-listers be pushed aside for lesser tier characters, all I'm saying is that the Joe team has a great variety of characters to choose from and Sideshow should consider all of them for 1/6th figures. How do you know that Sgt. Slaughter won't sell? that's highly bold of you to assume that Sgt. Slaughter will "destroy" the line.
Lissen, im a huge joe fan(toys/comics/cartoons), and i love the diversity of joe...but , certainly with joe, ya gotta go top tier figs for awhile before even thinking of going background.
here is an easy list they need to make before the other third/fourth level joes:
duke
scarlett
baroness
gung ho
lady jaye
destro
major bludd
crimson guard
flint
firefly
roadblock
ROCK 'N ROLL
shipwreck
all of the above i believe would be WAAAAY more popular than a sarge, far more recognizable and i think desired. There are just too many figs that should be made without question to 'throw a flier' out on a goofy choice for the next fig to be 'chuckles' or someone.
SW can get away with goofy choices like bib fortuna or (3)(!) endor troops, i dont think joe has the SW fanbase to be able to survive those bad choices...
i dont have a prob if they make 100 diff joes(wont be able to buy them all though ) but ,if given a choice, the main ones are way higher on my list to risk them not getting made if the line fails for bad choices...