Books aren't the Window to the World anymore
Younger folks don't read much. They didn't grow up being entertained by books.
When I was a teen, we had three TV channels and no internet. Reading was a great escape and adventure source for me. Jump back to Now, and there's the Internet, cable TV, thousands of offerings pouring out at you.
Never again (in the West) will kids grow up with books being their window to the world. Reading is the also-ran these days, merely one function on the multi-use widget young folks want.
To older folks who love reading an e-reader is best, since it does that one thing perfectly. To younger folks whose primary interest is shiny video and Faceborg, tablets meet their wants better.