While access to textbooks would be nice, it wouldn't need to be a major selling point. If the book is for a class in my major, I want to own a copy so I can use it as a reference after the class is over. And used textbooks can be had for a decent price. I just paid $40 including expediated shipping for a circuits book. The book is in great condition, and I am happy with my purchase.

And renting textbooks is pretty expensive, especially for older books. I bought a different used textbook for around $15. The book is in great condition, and renting it would have cost $40.

It would be hard to maintain, since a lot of textbooks change version number relatively frequently.

Yes, there are quite a few, actually. But they usually don't give you significant advantages over the old buy new/sell used model.