Board Thread:Naruto Discussions/@comment-5054236-20150717003436/@comment-26143131-20150718200759

Well... The only reason I see for Narutos lack of Rinnegan could be his lack of the Eternal Mangekyo Sharingan. I find this the most viable explanation: It shows us why shinobi like Obito and Danzo with both the Sharingan and Senju DNA haven't gained the Rinnegan. It also explains why Indra only possessed Hagoromo's spiritual energy. In order to obtain the rinnegan he might've needed the physical energy of Asura. Thus Sasuke was able to awaken the rinnegan because the half of Hagoromo's he obtained contained the physical energy required to evolve it.