The reason for that is precisely because laws regarding digital library content distributions haven’t been updated to reflect the digital age. It would be far more common if digital content was treated similarly legally to physical content for libraries, but the fact it isn’t is directly exploited by publishers and digital content companies. You might assume since it’s a digital file that it would be forever, but arbitrary fees and limitations that physical library content legally cannot have been (and are) consistently applied to digital library content. Especially ebooks and audiobooks. From circulation number-based expiration (file deletes itself after three patrons check out, etc), date expiration (file auto deletes in 3 months or whatever number the publisher wants, for example), price gouging by publishers (ebook prices and audiobook prices are often triple the normal library book copies), and the most annoying of all, time-based restrictions. When new books are published by larger publishing houses (especially hyped books), libraries are often limited to how many digital copies they can buy for a period of time to essentially try and force patrons to buy the books. Different publishers have entirely separate policies, and some are just on a book-by-book basis on how much extra money they can squeeze out of libraries. Believe it or not, Disney’s book publishing arm actually tends to have the fairest pricing policy of most other larger publishers.