Just like an infant learns to speak. Just like learning to sight-read. This little myth is sometimes perpetuated by players who are weak sight-readers. So are legions of fine musicians who are nameless. But life is too short.
Music is too big.
And good sight-reading can save a great deal of time. All of the balance, highlights, contrasts and symbolic meanings make sense immediately - all in the great dark room of the mind. To a good sight-reader a page of music is like that. And virtually anyone can learn how to do it. We are not trying to be clever or glib.