In addition to some of the great comments so far I want to add. Playing soft requires more control so it does require spending time to get better at it. Remember that playing soft require less volume of air but the same QUALITY of air (support). I find it helpful to think of blowing through to the next note to keep the quality high. When we practice soft playing it makes our embouchure not as muscle bound as loud playing does. makes it more responsive, Efficient. Improves tone and actually helps our sound and control when we do play louder.