"Refuse to sell..." and "have no supply.." are two different things.... I'm sure that Ford (or any other manufacturer) would be happy to have a ready supply of parts on hand for 15... 20... even 30 years. But only if consumers would bear the financial burden of this kind of overhead.... And I can see that happening. Additionally, most forget that a $2 part can get handled, stored and shipped enough to turn into something that has an aggregate "cost" far in excess of its perceived value. Ain't nobody here that does much for free... can we expect another entity to see things differently?
As another reply points out.... you have a "fringe" market vehicle.... The Aspire and similar have two purposes in their lifetimes... they fulfill a "niche" market and they play a role in achieving CAFE standards...
What may be an alien term.... "supply and demand".... If there is little demand for something, it wont be supplied. OTOH, if you owned one of the popular vehicles, you will find thet there are still parts "in the system"....
FWIW, if the parts you seek have even a modicum of desirability, the aftermarket would jump at the chance to supply them.... for many body and crash parts, the aftermarket will offer reproduction or NOS parts... if yours isn't popular, you will find out about "econobox"...
Even the Japs will only offer a finite supply of parts.... the money is in new cars...