Doesn't it mean a lot of effort to develop Android for an eink product? You wouldn't want all those android effects like when changing from one home screen to another or when opening the drawer etc. So you'd have to disable all of them manually. Besides that you would have to remove all those apps, preferences and internal modules for sms, phone, camera, gps etc etc
Porting Android to an ereader seems to be mostly about _removing_ stuff. And it's a lot of stuff you'd have to remove... If you create your own firmware from scratch, you will only be concerned with the user interface. Everything concerning modules/drivers is the same effort for Android...
If you plan to keep your software very slim (because ereaders have bad hardware specs), it doesn't sound so clever to take Android and strip nearly 80% of it...
I actually didn't understand in the first place why there actually are some brands like Sony that chose an Android platform for their devices...
(btw, the effort put into getting android to run doesn't seem to pay out: 80% of apps simply won't work at all:
http://www.androidpolice.com/2011/10...e-ink-display/)