Because they’re not available as an e-book, and won’t be, for the foreseeable future.
When it comes to content that isn’t legally available digitally my mantra is the same as it is with any other out of print media: if you won’t let me buy it, I won’t feel bad about downloading it for free.
I already own physical copies of all of these books. That means that I am entitled to read them however I please, right? Why shouldn’t I head over to #bookz or demonoid and grab a copy that someone else (with a kind soul) has taken the time to digitize.
Is it theft for me to download a digital copy of a book for which I own a physical copy?
(Is it theft for me to download a copy of a computer game that has been out of print for 25 years? Is it theft for me to download a vinyl rip of an LP or a single that was never released on CD? Should it be?)