Or maybe the textbook could focus on the important theory that needs to be covered, and leave keeping up to date with the newest fads up to the students and the

Or maybe the textbook could focus on the important theory that needs to be covered, and leave keeping up to date with the newest fads up to the students and the professor teaching the course? The theory is what gives the textbooks value. It's the timeless and constantly useful material that makes a textbook worth referring to decades later.