You are so right of course. Here is the start of another (challenge worthy) misunderstanding.
I don’t advocate miking instead of singing. If the singing is rotten, no mic kan save the show.
But I think that the mic is the distribution part, therefore part of the instrument.
To catch the voice in the most favorable way, you have to be aware that using a mic is a technique in itself.
Frank Sinatra was known to get really pissed at people he could hear breathing in the mic. He told repeatedly that the people (women mostly) he caught breathing in the mic didn’t have a clue about the instrument. Untill his daughter did it and then there was little comment left. He himself breathed in through the corner of his mouth.
So yes, singing is very important, but nowadays we hear nothing without a mic.
Kind regards, Gus