Because if I do not use my photocopier it does not emit anything, it just emit things during usage. In contrast I do not "use" my wall. It maybe emits things when it is newly made, but otherwise it does not emit things.

The same arguments was true for asbestos as well. Asbestos building materials are totally harmless if left undisturbed. But eventually that wall will have to be be repainted/sanded/drilled into/knocked down.