Gosh; I don't know - perhaps becuase they had split into the Northern and Southern groups?
Because Kings are a record of one group and Chronicals are the record of the other?
Ez. 37:16.
"Son of man, take a stick of wood and write on it, `Belonging to Judah and the Israelites associated with him.' Then take another stick of wood, and write on it, `Ephraim's stick, belonging to Joseph and all the house of Israel associated with him.'
BTW; it's EPHRAIM's stick: NOT Joseph's.
Well, when you do know, lets chat.
And, yes, it is Jospeh's stick, but it's in Ephram's hand. (Joseph's progeny) 19 Say unto them, Thus saith the Lord GOD; Behold, I will take the stick of Joseph, which is in the hand of Ephraim, and the tribes of Israel his fellows, and will put them with him, even with the stick of Judah, and make them one stick, and they shall be one in mine hand.
They are indeed one in the Lord's hand. The bible, given to us from the tribe of Judah testifies of the divinity of Jesus Christ, and the Book of Mormon from the tribe of Joseph, is a second witness of Jesus Christ. Cheers