If every teacher gave this kind of advice to their students, students would be more motivated to learn. The problem is that most teachers don’t understand their purpose, or they just don’t care enough to give it any attention. If a teacher only answers one question correctly in their entire career, it should go something like this:
Student: “When am I ever going to use this information? I’m never going to have to do this stuff in the real world! These exercises are useless outside of this classroom!”
Teacher: “You are correct. It is quite likely that you will never directly apply any of these exercises outside of this classroom. Their purpose is to coach your mind’s thought process. These exercises make you think, and over time they will train your mind to think more efficiently. The only purpose is to build your problem solving capabilities. You may never be asked to solve a complex factorial in the real world, but if your mind understands how to solve these problems, it will be more equipped to deal with the complex problems that do exist in the real world. And believe me, the real world is filled with problems that need to be solved.”
Update: The people who feel that indirect education is pointless miss out on the fundamental concept. While students may not use the specifics of every lesson they learn in school, every lesson does expand the core thought process of the student’s mind. Over time they develop problem solving skills that are universally applicable. No single lesson can teach this, and no single lesson is more important.