Earlier quoted context omitted.
You've never seen a paperback made in the 1960s-1990s? The paper is brittle and the pages are literally falling apart. You can't read paper where pieces of it have fallen off and disintegrated.
I have many paperbacks from the 1950s to the present day. Some of the really old ones are a little yellow around the edges, but brittle and falling apart? Never. I have no idea what you are talking about.
How often have you read them? Many of my most beloved cheap paperbacks from the 80s and 90s have been replaced at least once since they've literally fallen apart as I was reading them. Also my books from the 50s and 60s seem to be of higher quality than books from the 80s and 90s (or that could also just be survivor bias).