You're absolutely right, which is why the IA buys physical books, scans them, and makes them available online under so-called "Controlled Digital Lending". Renting out one digital copy at a time is covered by fair use, they argue, although it hasn't been tested in court.*

* That is expected as a part of the publishers lawsuit against the "National Emergency Library"

https://en.wikipedia.org/wiki/Controlled_digital_lending

https://en.wikipedia.org/wiki/Internet_Archive#National_Emer...