As an ebook consumer, the single biggest reason I don't buy more ebooks is because I have to spend time and energy figuring out if the ebook has DRM or if I can remove the DRM afterwards.
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.