alt Hacker News>Hopefully you can infer how this tracks to the written world and primary sources for language, technical manuals etc etc.
I honestly can't and I think you can't either or you would have used an example with books/printed media rather than film, an entirely different ballgame.
OK... I'm going to assume good faith even though your wording makes it somewhat unlikely.
Similar textual examples would be any text containing actual language as it's spoken in a given place or time. Or any factual textbook detailing the buildings present in a given location. Or any text book detailing a now defunct construction process. Or any text book (generally small run) detailing a niche interest, now missing ecosystem or the state of a particular political situation at a given time. Essentially all textual primary sources for events which are not currently considered important - but which we have no way of estimating the future importance of. One can continue to create countless counterfactual examples in this vein. My overall point is we cannot know what may be useful or even essential in the future, and knowledge should be preserved under the assumption that it is likely to be.
Historians frequently refer to this paradox - how everyday aspects of life are frequently not explicitly documented, since they're so obvious to the communities or communities of expertise that observe and carry them out. So it's actually incredibly important to preserve what seems like ephemera.
Hell we couldn't have AI training at all if we lacked the corpus of existing written literature - but there was no way any author could have anticipated this future utility more than a couple of decades ago.