Music theory, at an advanced level, is no more about rules than physics is. It's descriptive, not prescriptive. It's about why, acoustically and psycho-acoustic

Music theory, at an advanced level, is no more about rules than physics is. It's descriptive, not prescriptive. It's about why, acoustically and psycho-acoustically, certain practices result in the sounds they do and why we perceive sounds the way we do. What rich or successful musicians do has as much to do with music theory as what rich race car drivers do has to do with physics - the car is the result of generations of the study of physics, but the driver only needs to know how they bits they interact with work. The fact that the vast majority of players have no idea how the intervals of 12th root of two to the 4th power, or 5/4, became a Major 3rd (ET and JT respectively) is irrelevant to a discussion of theory. I could teach a semester long course on how we arrived at our current notes on the piano keyboard, but lots of A-list piano players don't know any of that. A physicist is the equivalent of a music theorist, not of a musician, as music theory is largely applied physics and geometry applied towards acoustics.