Librarians aren&#x27;t subject matter experts on these technical fields, so it is very hard for them to know if a work is still relevant.  They may be inclined to keep the &quot;Learn Excel Today (now updated for version 3.0!)&quot; because they know people still use Excel, while the Art of Computer Programming looks like a relic from the 70s that surely can&#x27;t still be relevant, right?