The real reason to develop your music literacy is to help you practice.
I’m working on the tenor part to several challenging pieces right now, and I repeatedly find myself thinking about how I would have practiced them differently in college.
Back then, as I was developing as a musician, I would brute-force practice. Straight repetition, hour after hour. Now as a secure musician with an emphasis on literacy, I have a lot of context that I can use to be more efficient in my practice.
What is the form of the piece? What part of the chord am I singing? Does this section come back identically later? What is the rhythmic framework and what musical tradition does it come out of?
I have ready answers to these and so many other questions, and the answers help me practice so much more efficiently.
It reaffirms my intention as an educator and director to help my students see that context, regardless of their musical literacy skills. The more context we can acquire, the faster and more effective our practice can be.
That’s a mighty strong reason to engage in developing your literacy.