But I'm Not Going to Be a Professional Musician, You Say
So you say you're not going to be a professional musician? Cool. But you should still practice.
I am not a professional mathematician, but learning algebra helped me practice thinking logically. I am neither writer nor librarian, but studying literature at the feet of competent teachers helped me think critically, appreciate ambiguity and irony, and delight in the ways skilled writers point to the poignant or the ridiculous. And I do love the ridiculous.
Because all of my various training has shaped how I interact with the world, I use it all the time. I can't not use it, in fact. It is part of who I am. Worthwhile pursuits have improved my well-being, my relationships, and my art. And the arts connect humanity across generations and cultures, helping people to understand and to feel understood in ways that nothing else can. This is no small feat.
It's true that most folks who do music are not professional musicians, but doing something inherently valuable for money is hardly the best reason to do it. So, if it's not too early to ask, what do you adore with a fiery passion? Music? Awesome! Something else? Also awesome! I can hardly wait to see all the things you'll do. The world needs engineers and doctors just as much as it needs artists.
No matter what else you pursue, you will never, ever, ever be sad that you are musically literate.