The Old Testament is composed largely of three kinds of writing: The Torah; the subsequent history of the Israelites and their relationship to God; and the prophets. Confusing one for the other will lead the uninformed to all sorts of misconceptions. And we know that it was written over a period of about a thousand years, so it naturally speaks with many voices, some of which plainly include myth and allegory as well as actual history. Not to mention poetry and song.
Good point - also the history books are not quite Herodotus level history