Yes, digital textbooks can have all those nifty things, but usually don't. And cross-referencing something in a digital textbook? Forget about it. In a paper book it's so much easier to flip back to check something out than in a digital textbook - even more so if you're quickly flipping back and forth comparing passages, or comparing between books. Textbooks work in most lighting conditions, don't need power/recharging, and don't have reflections of the overhead lights to distract you.

They both have their pros and cons, but the actual experience of digital textbooks falls far short of their promise.