As someone who learns far better by lecture, I've always been bemused by the concept of textbooks. I've never thought that the several hundred dollars I paid for a book got me nearly as far into a subject as listening to the professor.
But do you really think that a lecture can cover material as thoroughly as a textbook? In my experience, lectures were supposed to cover part of the material (perhaps some of the trickier parts), but could never be treated as a substitute for reading.
But generally speaking, especially when you account for the probability that "read the textbook" will result in me either grinding to a halt or just having content slide off, I covered more in lecture.
Textbooks were useful for specific needs for depth, used much more like reference works than a way to learn an entire topic.