So I heard a rumour that the reason the cover they sent to reviewers isn't for sale is that they didn't get very good feedback on it from the reviewers or the public reading about it.
So, they went back to the drawing board for a more versatile cover, one that serves as a stand as well as a screen protector, and it simply wasn't ready for mass production on launch day.
TL;DR: Patience, good cover coming from Samsung/Google, and of course a plethora of covers from third parties.
The book cover case for the SGT 10.1 devices was actually not bad in my mind. I'm holding out hope that Samsung or Google can make something similar and better.