Parents have this broccoli stuff they've decided is Good For You, and make you eat it. They don't listen when you say you prefer steak.
Schools have this Educational Method (including homework, tests, textbooks, lectures, etc) they've decided is Good For You, and they have the Right Answers (which are sometimes wrong), which are also Good For You. They make you eat it. And they sure don't offer steak.
PS you can tell textbooks are worse than real books, because when real people (not students) go to a bookstore to buy something, they don't choose a textbook.