Board Thread:Naruto Discussions/@comment-26090777-20150217192231/@comment-756329-20150219134222

Man of Sin wrote: They weren't thought of until Part 2. They were just plot devices to make the Uchiha clan more relevant. Kishi doesn't care about them and ignored them, just like with tge Uzumaki and Hyuuga. Thank you for stating what we're all thinking.

Seriously though, the reason we don't see any Senju is because unless your name is "Uchiha", you don't have a backstory at all. It wasn't until "The Last" we got ANY backstory on the Hyuga and other clans; a trend that will hopefully continue with the other clans now the Uchihas are irrelevant.