To take a crude example in a different medium - new york in the 90s - widely documented right? Yet, if you want to find high definition video of street life in a given burrough on a given day or year, you're faced with an enormously difficult task. There were some HD test videos done in Manhattan in the late 90s (which have been posted to Hackernews before), but there's no equivalent for the other burroughs. Your best best would be finding original negative out takes or location scouting footage from feature films, a very hard task. That's only 30 years ago. Outside of the focal points of the worlds attention - English language, rich countries, places in the news, contemporaneous sources for 'non notable' events (lifestyle, how people spoke dressed etc) is surprisingly poorly preserved.
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.
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.
1. If someone is acquiring books in bulk for bargain-bin prices and shredding them, they're books whose physical copies have essentially no market value and which, absent this buyer, were overwhelmingly headed for pulping or landfill anyway. Millions of books are destroyed every day.
Could one of these worthless looking books turn out to contain information historians care about in a 100 year? Sure. But that doesn't create an obligation for someone to pay to warehouse every extant copy forever. Physical Preservation has costs: space, cataloguing, handling, transportation etc. Archives and libraries have always had to make choices for this reason.
2. I'm not arguing that preservation has no value. The question is whether destroying a physical copy after digitizing it is a serious loss when talking about mass-produced printed material.
Was this the last surviving copy ? Is the information unavavilable in libraries, archives, other editions, scans, citations, contemporary works etc ? If not, nothing has been lost except one physical instance of a reproducible object.
Your film analogy worked a lot better because old film footage is often unique primary source material. A camera recording of a random brooklyn street in 1993 may literally be the only recording of those people, storefronts and circumstances. The nth printe dcopy of a technical manual is not analogous to that.