It is because lots of people don't understand that eInk is easier on the eyes. All they see is side-by-side features:
- Color vs. B&W
- Can read in the dark w/o an additional light
- Cheaper, for the feature set
I think a lot of us read all day on LCDs or CRTs, which are essentially light sources. This creates a lot of eye strain over a period of hours and hours. It's like looking at a dim light bulb for hours at a time.
Don't worry, they'll wise up some day.
For reading, I don't think color eInk is necessarily an advantage. I'm not anxiously awaiting it. It is going to come with a big price hike too, I'm sure.