Board Thread:Naruto Discussions/@comment-25358381-20140903032737/@comment-24531362-20140903050435

If every Uchiha can use Fire Release, but not every Uchiha awakens the Sharingan, then there is no link. It has been stated that not every Uchiha gets the Sharingan, because otherwise there would not be stipulations for its awakening. Similarly, use of Fire Release does not lead to use of Amaterasu, as in the case of Obito.