Not every musician or music student needs to learn scales.
To strum guitar chords on your favorite song, you don’t need to know scales. To understand the chords you are playing—you most definitely do. Attempting to read music fluidly without knowing scales can be awkward and frustrating—it doesn’t work. To play a funk groove or rock riff, you don’t really need to know scales. However, to be a versatile and competent player in most styles, you do. It all depends on how far you want or need to take your musical endeavor.
There are lots of scales, and you could learn a few or many—whatever is needed. A scale is the basic vocabulary of music. You can learn to speak a little bit, or a lot.
A person only needs to learn what they need to know, in order to play or write the way they want to play or write. That’s all. It’s actually quite simple.
(A note on talent and education: I had the pleasure of having a pro songwriter as a student for a few months. He was a singer/guitarist, and had a list of #1 hits that anyone could retire on. So why did he end up in my teaching studio? Well, this was a conversation from our first lesson: “I write a song for Willie or Whitney. Then I hear it on the radio and the chords are different and there are strings and horns and all of this other stuff. What is that? How does that work? And what is a scale, and what do the black keys on a piano do?” The man was serious. He was genius songwriter who had crafted that skill. He had a natural ability to create. He was an excellent communicator, story teller and guitarist. He had no musical education at all, and didn’t need one. He only sought some education when he became curious. Interesting.)