Probably because not many were produced. Something like 28,000 were produced in the limited span of years. And they're the easiest to build, with the long wheelbase, you can throw just about any drive train under it and not have to worry about pinion angles. Heck, with my setup, my driveshafts are still 32" and 33" long. They still rust out, mine is a prime example. If I had a CJ-7, I'd just go look for another tub, they're fairly common. But since it's not, I'm rebuilding mine, and with enough steel to make a battleship, and it'll be just as tough. I doubt I would have gone to this extreme with any other CJ.
JEEPN
'81 CJ-8 Scrambled!
GM151/SM465/NP205 twinstick/7"Lift/33"TSL's/IHC D44's 4.10's Lock'd