The perception (or rather misconception) seems to have evolved unfortunately, that music is a supplemental activity - beneficial, to be sure, but a luxury outside the "core" curriculum.
In truth, however, musical training develops innumerable skills and cognitive processes that are applicable to a wide range of disciplines. Whether or not a child grows up to be a professional musician, that child will have been better prepared for her career having studied music than not having studied music, even if she chooses to become a doctor or an architect or an archaeologist . (Please see Brian Pertl's outstanding blog post Everything I Know About Business I Learned at the Conservatory).
It is therefore important to think of musical activity as curricular rather than extracurricular. I my mind, the distinction is this: curricular activities are non-negotiable. Children are expected to complete their Math homework - even those children who will not become accountants or engineers. A conscientious parent does not allow her child to blow off Math or Science or English homework, simply because the child doesn't feel like doing it, or because the child has soccer practice or ballet that evening.
Daily practicing and listening should likewise be non-negotiable. It is each Suzuki student's ongoing assignment to practice what his teacher has worked on in the lesson, to practice review repertoire, and to listen to the reference recording. He may not receive a grade for cello lessons, but as we know, the grade isn't the point of studying Math, and neither is it the point of studying music. In order to reap the greatest benefit from musical training, regular follow through is vital.