The importance of this alone dwarfs all other reasons! I have books that will never be on the Internet; and, they are critical works for both literary and life-sustaining reasons.
Internet works are typically shallow, certainly not all-inclusive. Many of them are circular links to incomplete material.
One case in point: Microsoft software documentation had usable content when it was organized and printed on paper. Their paperless documentation is mostly useless.
This goes on and on: There are no decent Internet materials regarding the machine shop or wood shop. Oh, there is a lot there, but not the in-depth quality of some of the 1900's books on the subjects.
The "promise" that "someday" the net will have ALL books ( yeah...right...LOL ) on line, is a LIE! Some of the books I have were privately published, in limited editions, with hand water colored illustrations, well over 100 years ago and no way will they EVER be put on line. And I know this, because these were rare books books to begin with and not many of them still exist. They are literary treasures, to boot.
And you hit on a different kind of book, which is valuable to you and probably others, too.