We know nothing about the people who died during the vesuvius eruption without the castings. The ash hardened around the dead bodies, which eventually decayed. You can't access or see the people because the empty cavity is encased. Only through inhabiting the emptiness with plaster can we see and know something about the bodies. I think the same is true with architecture. I think Maison Bordeaux is a good architectural example. The floor is only complete when the lift brings the owner to where he needs to be. Otherwise, it's not complete, lacking the inhabitant it's made for.