As I understand it, the term "basket case" means the car was dismantled by some would-be restorer, who then never got around to the restoration. It is quite different from a "parts car", which is a car that is probably not worth restoring due to condition and/or incompleteness. Between a "parts car" and a "daily driver" lies a large spectrum of possibilities. In regard to our cars, of major consideration would be completeness in general, engine condition (if there), softtop presence (as mentioned), and condition of body and chrome. (I'm not gonna talk about what is restorable vs. what is not!
And, as for basket cases, if something is in pieces too long, parts tend to get lost and discarded, so even a "complete basket case" may have major parts missing.
This probably doesn't help the discourse much, but when I read the thread opener, I thought it might benefit from some additional detail.
Joe, getting in gear to organize and catalog several dozen motorbike basket cases....