> Like if you just excepted owner-occupied housing you would already have exempted most of the housing stock in the United States.

Because the purpose of this isn't really to get money out of owner-occupied housing, but out of industry; and in particular, as the top-level comment in this thread, to make "intellectual property" more rational. If Sony / Disney want to keep copyrights on those 30-year-old titles, they need to keep paying enough to prevent a team of enthusiasts from getting a big enough Kickstarter to buy them up and make them public domain.