Why Do So Many Schools Treat Music as a Non-Core Subject?

Below you will find a video from Daniel Levitin of McGill University, providing some discourse on the importance of music to human development, including the interplay of music and movement of the body, as well as neuroscience. We continue to learn so much about how the brain works, yet, in so many of our schools we have yet to apply this research to our programs. For example, based on Levitin's research (you can read his book on This is Your Brain on Music), I would pose the question: "Why do so many schools treat music as a non-core subject?" It seems counter-productive, and it would support Sir Ken Robinson's assertion that schools today kill creativity. Furthermore, if Dan Pink (blog) is right in asserting that creativity should be a hallmark of a 21st-century education, then why aren't more schools exploring this?