Given there is a contentID system for explicitly copyrighted works, it seems insane that nobody involved in these systems has seen fit to do the same for explicitly public works.
These systems are good at picking up small portions of copyrighted works within some larger context, but to guarantee that 100% of a YouTube video or scribd document is in the public domain is a different problem.
For published works like the Mueller report, one wouldn't need contentID. Matching the document's hash would suffice.
A hash would still only work for the exact document. Suppose someone uploads a new version with a better table of contents, or with some added annotations [0]; now your hash no longer matches, while contentID probably will.
[0] Both things which could be copywrited, but I'll assume will not trigger the actual flag.
There is an excellent profit motive, it is just not as directly obvious as it is mostly realised in money not spent and humans seem notoriously bad at preferring small gains over large savings.
Not doing it incurs a fairly large cost across many areas of the economy. Time has to be spent by people faffing around with this nonsense that creates no wealth economically and this essentially creates an overall drag on profitability across most of the economy, parasitically favouring only small sectors such as legal services.
The trouble is, this is a group profit motive and people seem to think of profit motive mostly from an individualistic and zero-sum perspective.
