The first sentence of the wired article linked should help with understanding. There are concerns about the need for software updates and the lack of replacement parts/maintenance, meaning it goes from collectible to paperweight
This probably wouldn't be as big of a deal in decades past. Worst case, you just had to learn how to do car maintance yourself, or take your car to an expensive mechanic that worked on oddities. But now? When almost everything is software controlled, and the company that controls that software disappears and takes their keys with them? You're screwed.
That's what OP is confused about - why anyone would buy an experimental car without knowing it has potential to be worthless. The lack of parts on a novelty ice car has the same issue when the company folds.
Not all of them - my last two went up in value towards the end as collectables (ferrari 308, mk1 mazda mx5). They start getting a bit expensive to maintain after a while though.