Small publisher here. I believe Ebook sales have been generally flat or declining for many titles for the following reasons: * Pricing issues * Huge influx of new/republished titles entering ebook distribution channels are outpacing demand, including many free or low-cost self-published titles * Kindle Fire sales negatively impacting ebook reading habits encourages people to do other things besides read (video, apps,…
Also, I spend time thinking about the fact that if I ever move to Kindle, any epubs I have won't work regardless of DRM.
I can't speak for other readers, but this is why I don't buy or read books as much as I used to. And I used to read a lot of books.