You have a point. For someone designing phones and other gadgets, this would be a boon. And since it's full color and probably limited run printing, it's pricier.
Well, I just wanted to hate on Apple a little bit. All done now.
Yeah. Thing with design books is that the book itself is usually a presentation of whatever design aesthetic in and of itself. The paper stock, the binding, the colour grading on the print. I've had a few graphic designer friends try and explain why all of this stuff is important to me over the years but it flies over my head.
But you can guarantee there somebody somewhere will write a blog about why Apple chose the stock it used for this book...