Why is music manga a thing?
>tfw no imagination
Because it's mainly about the story and the characters, situations and emotions.
Also it's like a silent protagonist in an RPG. If he has a voice and personality you might not like him because you're forced to follow his character.
In music anime you might not like the music and lose interest, meanwhile in manga you'll just get hyped because of the characters interactions between themselves when singing/playing that music and the emotions it makes the public or other characters feel.
Imagine Kuyuki starts singing generic pop 101 LiSa, it would kill my interest in BECK. The anime did well but the manga is still better with how it deals with stuff for what I said before, characters and their reactions/interactions when the music is happening.
Also another example in BECK.
Kuyuki's voice after he peaks his skills and shit is supposed to be fucking god tier. Yet in the anime his voice is not that good as the story makes it out to be.
Also Devil's Way is supposed to be a GOAT tier song that makes you cum in your pants while listening, but would an anime version make it justice? I don't think so, we're talking about a music that made everyone in the world hard.