Every year some get restored. Very cool. Some get a new motor. cool. More get parted out or crushed. Bummer.
Still a ton of them on the roads out here in Arizona. Everyday on that list of Craig's there are some for sale and parts.
Eventually they will become more and more desirable.
I started with one and over the years picked up a few more bodies. Doing a 78 S.B. right now.
As to your original question of why do people ignore square bodies; I would say if they are ignored it is by those who drove em (or still drive em) as "old work trucks". Hard to think about dumping serious money (for lots of folks) into an old work truck. Till they get scarce.
