Asking vocal students to knuckle down and learn to read music sometimes seems like a hard ask, particularly when so many of them are doing so well without it. A print-out of the lyrics and a familiar melody make it so easy to learn without needing to think explicitly about notes or rhythm or phrase.
As a teacher, I have a big emphasis on music-reading because it gives me something concrete to use. It is so helpful to be able to point to a note and say “this goes for four beats”, or “breathe before this melisma or you will run out of breath”, or “this note is A, you’re singing it G#”. The benefit for the student is the ability to participate fully as a musician, using the vocabulary and the technical knowledge to understand and convey ideas and thoughts about music.
Below is a screenshot from the website Music For Music Teachers with some thoughts on vocalist students learning to read music.