This isn't an ebook story, but I've had my hands on BBs, and they interest me. Also, you can read on them, which is good enough for a post.
I know one reason why BB should do it: the untapped market. RIM now have competitors offering a similar service on Android and iOS. RIM probably realized that it would be better to risk losing some hardware sales rather than risk someone coming up with a better competing service.
Also, some of us like the service but don't like the hardware. I've done setup and basic tech support for BBs, and on one job they offered to give me one, brand new. I declined.
I don't like the general hardware design of BB. I think the keyboard on most BBs is too small, and so is the screen. I don't know why anyone would pick a BB over (for example) the 3.5" screen on the iPhone.
Actually, I do: the service. There's a reason why it's called a Crackberry.