First, teaching methods
First of all, the main reason is that with the development of our science and technology, most teachers are now equipped with multimedia screens, and most of what teachers have to say in class is explained by their own PPT, so why don't teachers use books? Generally speaking, not all the contents in the book should be told by the teacher. It will be more convenient for the teacher to do PPT with himself in class.
2. Is it all?
Are all teachers like this? Actually, it's not. There are still some courses based on the contents of books. Teachers will ask to use our textbooks, but there are few such courses.
Three. abstract
Then, with the development of science and technology, the way of telling books has been basically replaced by multimedia teaching, which can well fit the teacher's explanation ideas. Each teacher's explanation ideas are different, and he likes to cooperate with multimedia teaching according to his own ideas, which is convenient.
The above is my opinion on this issue, which is purely personal and for reference only. If you have different opinions, you can leave a message in the comment area to discuss together.