Here's another angle:
I was wondering, why haven’t we ever seen Miku as part of a band? There’s tons of fanart with Miku and other vocaloids holding instruments, singing, etc; but never is Miku presented as being part of a band. I mean, she’s never presented as a musician, that is, a performer whose music is deeply a part of them, unlike an idol who merely performs this music which external to any whacky definition of “self” you want to muster up.
I suppose the thing about the band is that there is no official Vocaloid anime by Crypton, where such thing could happen, and no Musicoids outside of it. You are welcome to write the software though, make it interoperate with UTAU.
As for idols who merely perform, I am going to go ahead and be very injured on behalf of... say, Yukiho Hagiwara, because she's the one who would cry if she heard such discourses (and if she were real, of course). Why do you think they printed "image" songs? Of course we're getting back into the whole "manufactured" angle, but look, if Namco goes to such lengths to give idols a personality, and fans observe how Makoto matures and becomes more and more femininie in every game (all the while remaining within her official age... like Bart Simpson who never needs to graduate the 10th grade, to quote Matt Groening), then there is a certain meaning to it, or at least an expectation, that is rooted in the way things work in reality.