Marketing

Some book publishers don't like the Kindle. Either they're afraid of it or they've crunched the numbers and they don't like what they see. (Some days, 95% of the top selling Kindle titles are free... demonstrating that digital goods with zero marginal cost and plentiful substitutes tend to move to zero in price).
Worried about the medium, they hold back, delay or even refuse to support it.
Which is fine if you have market power, but you likely don't. No publisher does, certainly. The Beatles couldn't stop iTunes from changing the record business by sitting out the platform, and there's no book publisher who can stop the Kindle alone.
It's tempting to look at a high-momentum market innovation, something that brings efficiency but leaves change in its wake, and try to stop it single-handedly. Tempting, but not so smart, I think. The market waits for no one.
The alternative to joining in is to sit out the game loudly. Don't just hold back your support, organize your peers. Create a (sometimes illegal) coordinated effort to stop innovation. I'm not going to bet much on your efforts, but it will certainly outperform a solo effort.
Quiet, passive-aggressive whining in the corner is both annoying and ineffective.