“It wasn’t expensive, but the cars had been sitting there for years and many were not museum quality cars, some showed the ravages of sitting without proper care.”
The reason is that museums are run by care-takers. The cars that end up at car shows are lovingly cared for by anal-obsessive-compulsives who love their show piece cars more than they love life.
Certainly they love their cars, and some are anal retentive, but thay have some fine rides.