Breathing is the connection between the mind and the body. When the mind concentrates on the breath, it focuses attention on the present moment. Breathing is the first step on the path to discover your spiritual nature. As you get the body to breathe correctly, the mind settles down, and that creates fertile ground to develop whatever spiritual nature exists within you.
It's a subtle thing, freedom. It takes effort; it takes attention and focus to not act something like an automaton. Although we do have freedom, we exercise it only when we strive for awareness...