Why wouldn't anyone think that the guns that started the "Tupperware Revolution" would someday be collectible?
No different than first generation Colt SAA's, early model 1911's, Model T's, original Star Wars toys, etc, etc, etc. There was a time in the history of each when you could literally not give them away.
Because they're so common and cheap originally, very few people worry about preserving them. They're used as tools or toys and discarded or junked when worn out. The surviving ones in decent shape become collectible over time.