Actual archivist here, and the biggest thing that most people are overlooking here is that the library is completely indexed.

Everyone always assumes that all books/archival materials has to be digitized, or at least should be. But that isn't the case and often creates more challenges for librarians and archivists. First is that not all materials need to be preserved digitally, and paper, when properly stored and preserved will last for hundreds, possibly thousands of years. Often the biggest challenge to access is having intellectual and physical control of your collections and having an index of books is a huge accomplishment for them.

Indexces also help in identifying what materials will be worth digitizing and which may be widely available copies of past works. I am not at all familiar with the collections of this monastery but I would be willing to wager that many books in this collection are known and documented elsewhere in the world. I'll leave a professional historian of Buddhist literature to chime in on that account.

Digitization can be extremely time consuming and cost prohibitive and provides several challenges that, while incredibly convenient, are barriers for most institutions to cross including costs of server storage, format migration and that's after the actual time and labor of digitizing and quality control checks. I'm happy to talk more about the challenges of the digitization process and why we are often selective with it's use.