Regardless of what instrument you play, music theory is an important part of learning an instrument. Just as we speak a certain language, we should also learn how to read and write in that language too. It's how we communicate musical ideas to each other, and how we further understand the music we play.
Although basic theory is incorporated into all our lessons, Music Theory is a separate component to learning a musical instrument. It is also a prerequisite for students to do Music Theory Exams when doing certain grades in the AMEB or ABRSM examinations on their instrument.