I was also skeptical of this claim but managed to find someone who explains it:

https://downtownbrown.substack.com/p/five-fallacies-ai-and-d...

It's not that individual companies buy all copies of a given book, but that there's more than one book scanning company, and they aren't sharing the scans with each other. The result: books that were rare but nevertheless easy to find for purchase (thanks to the internet) are now vanishing off of the market, becoming de facto no longer accessible to the public.

Here we have another entry in the long list of "things described on the Internet that never happened".

Where did you see they tend to buy all the copies? This comment is the first time I've heard of this.

Most old books that are rare and unpreserved are so because their value is marginal, so nobody has bothered to collect and preserve them.

But where did you hear that they’re buying “all copies”? And to what end?

what is your source?