My personal wastebook at home is so rare, it's unique. That doesn't mean it needs preservation.
Like I said, at this scale, there are no guarantees for anything. Very likely will there be a unique copy of an invaluable book or letter an the person feeding it to the scanner will not know and the book get destroyed.
Like did Icelandic author Þórbergur Þórðarson ever write an a book about Esperanto, and send the only copy of it to Halldór Laxness when he was in Los Angeles? I don‘t know, but it is certainly something he is likely to have done. If such a book exists it would be invaluable to both Icelandic culture and to Esprentists. It likely would have stayed in Los Angeles where nobody would know the significance of it until it ended up in an estate sale, a used book store, and then finally destroyed by an AI company never to be discovered.
My hypothetical is just one of trillions of possibilities. At this scale very likely several of these possibilities will unessiseraly remain unknown unknowns forever.
Your what now? Made from your personal waste? That does sound unique.
https://en.wiktionary.org/wiki/wastebook
Oh right. But anyway, nobody knows what needs preservation, it's a basic problem of life, somebody usually mentions the BBC throwing out boring old Doctor Who tapes to save archive space because nobody liked it any more at that point in time. Some things should probably be thrown out now and then, I suppose.