If the course prof wrote a book on the course subject, it will likely be on the list. Many dissertations become books. The reading list recommendations are influenced by the politically "correct" views of the day. There are texts that are classics Shakespearean criticism has probably been done to death, but there new things to say in science and history
The requirement of a college course having a new book depends on the lecturer or professor. This depends on if they find the book useful in the particular course incorporated for your learning process.
You can't generalize. If it's a literature course, they probably have the same books every semester, but if it's something more technical or where the content changes easily, it might be new book every year.