When a woman gives birth to a child, the child needs to be able to digest the mother's milk; but when this child is old enough to begin to eat other foods, there is some switching off of this ability to consume milk.
Homer's whole language, the language in which he lived, the language that he breathed, because he never saw it, or certainly those who formed his tradition never saw it, in characters on the pages. It was all on the tongue and in the ear.