I don't know why the old stevens shotguns are not appreciating. When I was a kid a neighbor had a side by side stevens. He would let me borrow it for small game. It was one of the best shooting guns I have ever shot. He still has the gun and it still is in good shape.
Stevens never had a premium line of shotguns. Nor did they win military contracts like Mossberg. They never did anything to make them legendary. All stevens shotguns do is shoot well and last a long time.