As the great economist Milton Friedman once said: nothing is free.
Expanding the library is a very large undertaking and dedication of resources like that would need a legitimate REASON. But right now Teary just can't think of one. The old books are still right there in the Hall for anybody to read (even if they willingly choose not to), so there is techically no pressing NEED to expand the library (othe than apostates whining that they want old publications). The "we aren't allowed to actually use the physical library" excuse is moot as well, because Teary used the physical libraries of several Halls for years whenever he wanted to, and he saw many others doing the same with no problems.
p.s., Bethel headquarters isn't just full of a bunch of lazy slackers that wait around all day waiting for somebody to give them a project -- they are there to accomplish specific jobs in the most efficient way possible. They only have as many people as the work merits and no more. The Society's resources are also uses as efficiently as possible and yet there is still constant need (such as the 100+ million dollars a year they have to spend to support missionaries, special pioneers and such in addition to RBC projects, publishing costs, ect.). So to say that they could just click their heels together and magically have an expanded WT library is silly. Remember, it is not just as simple as taking a book and scanning it -- all of the text and scriptures from every publication would have to be integrated into the existing indexing and referencing system. Far more difficult than just putting together a normal book -- it would take a few years at least even if they did see a need for it.