I have this aversion to paying money for things I don't actually want. For the most part, paper books fall into this category.
If the publisher does not offer the goods I want (ebook), then I am hardly going to give them money for something that purports to have the same functionality but is missing several important features in that it:
1. Requires me to find extra storage space to house unwanted hardware (paper).
2. Requires me to use extra equipment in order to access any features at all in certain circumstances (switching on the overhead light at night).
3. Is either not portable, or requires me to organise transport facilities at my own inconvenience (try putting a two-inch thick fantasy novel in your trouser pocket and see how far you get).
4. Has only single-user capability rather than the dual-user functionality required in a household consisting of two rabid readers.
It's a bit like asking for a scientific calculator and being offered a slide-rule. You only accept the slide rule if there are really important calculations you have to do right now; otherwise, you find a different shop that will sell you a calculator, borrow one, or go without.
Luckily, publishers do seem to be catching on to the idea that ebooks are not just some techo-geek craze that will disappear in a year or two. Kindle-spotting is a bit of a hobby of mine in public places, and the number of people you see with e-readers has gone up massively in the last year or three. We are also seeing more and more authors' backlists being published. I tend to keep an eye on what's coming out on Amazon, and it's easy to spot the backlists: you see a whole clutch of books by the same author becoming available on the same day. I think publishers are also catching on to the idea that it's possible to make a bit of money out of the older titles that have been out of print or in the doldrums for years - if you look at some of the publication dates, ebooks are coming out for authors who haven't had a new edition of anything published in over a decade.
It is undeniably frustrating when only part of a series has been published as an ebook, or worse yet, when a new book comes out with no hint of an electronic edition, but I think things are improving. One wonders whether a watershed was J.K. Rowling giving in on the subject of Harry Potter ebooks - she had always been vehemently against ebooks; one wonders whether other publishers/authors decided that if she saw the writing on the wall in the advance of ebooks clearly enough to cave in, then it was probably not something anyone else could avoid. Better to give in now with good grace than find your book sales taking a hit as people who'd invested in a book reader wanted to spend their money on content for it? After all, unless you're a die-hard fan of an author and will buy their work regardless of format, readers are going to direct themselves towards format first and content second - if all you want is 'a book' and you have a reader, you'll probably look at the ebooks first.
That is, of course, the other argument. There's the almost ideological stance of the ebook advocate, but then there's the man-in-the-street who wants to get the best value out of his investment in a book reader. If you've just paid out £50 or whatever for a book reader, it's an embarrassing waste of money if you still buy mostly paper books.
I think we reached the tipping point a year or two ago: now, no matter how much kicking and screaming they do, the publishing industry is having to move towards ebooks. Personally, I think we will see the mass market paperback disappear eventually; the ebook will be the edition of choice for day-to-day reading, and the hardback for people who want a 'display' copy.