To be honest, I didn't care about the cover art on physical books much either. I'm all about the words.
But here at least... everyone knows you can hit the back button and usually see the cover.
Mobi books can't open at the cover because the cover is part of the metadata and not the "text" of the book. All a mobibook designer has to do is place an inline image of the cover on the very first "page" of "text" and tell it to open there. Voila... cover art.