[thaumasiotes]

In the case of a library, I would tend to suspect one of these scenarios:

- The first and third book are currently checked out.

- The library acquired all four books, but the first and third have been destroyed / lost / stolen by customers.

- The library didn't acquire any of the books, but the second and fourth were donated and the library chose to absorb them rather than selling or destroying them.

None of those are even conceptually applicable to NetFlix. I definitely would not expect

- The library has a limited budget, and considered that it would be better spent buying the second book than the first book.

Note that NetFlix's inventory of physical discs doesn't suffer from the same problems that its streaming inventory does. That is (most likely) because it's trivial to obtain the legal right to distribute the physical discs -- you just buy them on the open market, the same way a library does with its books. NetFlix's streaming inventory isn't "curated", it's not under NetFlix's control at all.