There is no guarantee that a title available as an ebook will be available world wide or available in both mobi and epub formats, so I agree with those who believe that insisting on ebooks for all is needlessly limiting.
For example, The Remains of the Day was the February nomination and it wasn't available as an ebook in Canada. Did John F consider that when he voted for it? Likely not, since it was available as an ebook for him. Does it meet his ebook only requirement? Obviously not. Since I wanted to read it, I voted for it anyway and got a paper copy from my library, even though I vastly prefer ebooks.
As sun surfer mentioned, the voting each month will separate the wheat from the chaff and if ebooks are preferred then they will win.
I use these nomination threads as book recommendations, I've scanned all the threads from the inception of this bookclub (and the other one) to find books I might like. Some of the non-ebook nominations will eventually be released as ebooks, so I'm happy to have those recommendations and I put them on my watch list.