Its because textbooks are usually more in depth than lectures can go due to time considerations, this is why any graduate program is 90% papers and textbooks.

Its because textbooks are usually more in depth than lectures can go due to time considerations, this is why any graduate program is 90% papers and textbooks. A great example of this is Andrew Ng's course, even though he is the co-inventor of LDA (complicated Bayes network) he does not explain Bayesian analysis in his course.