Board Thread:Rebirth: Applications/@comment-1875854-20141110174716/@comment-1875854-20141114002936

While the Uzumaki are a separate clan from the Senju, they are still blood related. Using that as a base, the Uzumaki would have no intention of betraying their own family. There's no interest in making the strongest clan your enemy. They were much more interested in protecting it, as well with their own clan.

And then soon after he was turned into a statue (Kachuu), so it's not like it was even possible then.

Hashirama was also known for giving people the benefit of the doubt even in extreme cases.