Board Thread:Theories and Speculation/@comment-3001903-20160813042916/@comment-732150-20160813043712

Because after Hashirama died, Tobirama started isolating the Uchiha from any decision making role as far as making policy went. Sure, he made them the police, but that means they only get to enforce the rules, not make them. Making an Uchiha a jinchuriki would have put too much power in their hands. There's also the fact after Madara and Izuna, the next Uchiha to awaken MS was already presumed dead and actively plotting against the village (Obito), the following one was publicly considered a traitor, despite still being loyal. Even if those weren't issues, jinchuriki tend to be related to Kage, and when the times came to have a new Kurama jinchuriki, no MS users around.