This is the 'academic' part about learning music, or mastering any instrument, if you may. But essential, and necessary, for any good musician. The most brilliant composers of classical music were masters in their understanding of music theory. They sought to expand, challenge, and even outrightly break the rules of theory through their written compositions. (Now you know, they didn't become famous just because they died.)
Part and parcel of teaching music is that each year, I have the opportunity to put some students through the theory examinations. Now exams are not fun for most I know, but teaching theory gets me quite excited. It is truly a fascinating subject, with plenty of intellectual concepts providing great stimulation for the mind. It never fails to amaze students when they first come to understand the circle of fifths, and how all the key signatures they had been memorising since childhood are all interrelated.
Theory is simply amazing because it is a language of its own. To put on paper the sounds we hear, to translate them from the intangible to something which can be recorded in written form. Sometimes in great detail, with a high level of sophistication. This is a language which like any other, takes years to master, and even more to fully appreciate the nuances within.
So students and teachers of music alike, never ever neglect this musical language in the course of music education. It may be all just black and white on paper, but without it, it would be hard to pass on the art of producing beautiful sounds of music, generations after generations.