> But a lot of those books probably wouldn't exist if the author couldn't make some money from their work.

I think that's at least a bit debatable. People thought that about (normal) libraries back in the day, but it ended up having the opposite effect.

Not to mention out of print books or academic books which is a big usage of sites like these, since lots of people prefer physical books and only reach for pdfs as a last resort.

Libraries spend like $2B / year buying books https://www.imls.gov/sites/default/files/2021-08/fy19-pls-re..., which is like 10% of the total book market. So even if no one ever bought a book because they first encountered the book, author, or genre in the library that's already a signficant difference

I think I agree, the FAR bigger impact on my book's sales was Google search deciding not to surface it in search results. Presence on pirate websites had no effect, and eventually I switched to the PDF as "pay what you want."

Can you imagine if we didn’t have libraries and someone tried to create them today? From publishers to right wingers, they would be painted as communist plots to destroy creativity.