In most cases, ebook is just a cheaper option. One can still buy the paper version if preferred.
I do not understand how you need to be distracted by the internet while reading an online textbook. It is YOUR fault if you allow yourself to go to other sources. You need to discipline yourself and learn to be task oriented. You are young and living in a digital world, surely you know how to avoid checking your email, social media et al while doing homework. Like eons ago when we needed to get off the phone and settle down to study. It can be done.
I don’t think reading online is a skill, I think it’s a learning style and those are inborn, not learned. I don’t like e-texts. I read a lot, and constantly looking at a screen gives me a headache. I also don’t like scrolling through pages online. I retain information much better with a physical text. I can remember what part of a book I read something in if I want to recheck it (on the left side toward the front, in the middle of the page on the right but further toward the back of the book, etc…) You can’t do that with a digital book. I’d have to print it out if I couldn’t find a paper version. That wouldn’t be very cost effective for me.
My children have been using e-texts since fifth grade. Cheaper, lighter, and greener.