The student question, “Why is this important?” is valuable in almost every circumstance when we teach. It’s not impertinent, it’s not impossible to answer, and it’s not a time waster.
Wanting to know why an exercise, rehearsal strategy, ensemble tradition, or assignment is important is not impertinent: in fact it shows higher-level thinking in your students, which should be rewarded and encouraged.
Wanting to know why it’s important isn’t impossible to answer: everything we do should be done with intention. If you can’t answer for yourself why something is important, then you should research it and answer later. If you can’t determine its importance after research, you shouldn’t keep doing it.
Wanting to know why it’s important is not a waste of time: discussing intention is a great way to build cohesion, sync thinking, and inspire more commitment from your students.
Encourage your students to be curious about the underlying motivation for the things you do together. If no one is asking, “Why is this important?” then you should take regular time out of rehearsal to ask it yourself and answer it in discussion.