Actually they sort of do: people make derivative works or compilations that become encumbered when something out of copyright is found to be in copyright again

Actually they sort of do: people make derivative works or compilations that become encumbered when something out of copyright is found to be in copyright again. Something which has happened thanks to nonsense like "common law" state copyrights and retroactive extensions. Of course, that's an argument against the practice rather than for it.