Closets, attics, basements, garages, storage sheds, self-storage units, etc.
And remember - many amateur astronomers have MANY old scopes they collect, still use occasionally, etc.
I know guys who have nice UNITRONS from the 50's, 60's and 70's. And have a cousin that still has a 3" Edmund reflector (yes 3" reflector, not a refractor) with a cardboard tube from the late 50's.
Many of these old scopes are cherished "collectors items" so you probably won't see too many at your local star party.
The guys at NEAF (when they have NEAF) have a good size "display" of older scopes. Mostly Unirons, but always a number of other old scopes as well - Cave reflectors, etc.).