One problem is the cost of these devices. The unit shown in this article sells for $1500. Another is the slow refresh rate, which is often-times fine for tasks like reading a large set of text (ebooks, entire newspaper sheets, etc), but might not be well suited for touchscreen use where UI elements need to react to user interactions in a timely manner. The project in the OP skips user controls altogether, meaning you can't actually read anything beyond the front page.
eInk is cool, and the technology continues to be developed, but it's still a niche solution applicable to limited use cases due to the slow refresh and high cost.
eInk is cool, and the technology continues to be developed, but it's still a niche solution applicable to limited use cases due to the slow refresh and high cost.