What about those students who define music as "playing what you feel" and often shun theory discussions? Art can express feelings. Without some knowledge these students wander about musically and consequently express very little. There are many skills to be mastered. I am reminded of something said by the great baseball philosopher Yogi Berra, " if you don't know where you are going you might wind up someplace else". Learning theory can give these students some direction and goals so they wind up playing what they feel instead of playing something else. As a writer studies grammer and vocabulary, an improviser and composer studies music theory: to find and master the tools necessary for the goal of personal expression.
A musician who only wants to "play what he hears" or "play what he feels" already has an idea about notes that sound good in a musical context. That idea is music theory.