User blog comment:KingJupiter/Laying Down The Law/@comment-4080775-20150628124811

Keiku can cross timelines, so he came to GD to help save it from Black Zetsu and co, and then before that, he acquires Hago's by absorbing it from another shinobi to awaken the Rinnegan in both eyes. That's my reason, and it canonically make, as Sasuke did the same thing, but with Hagoromo's chakra directly. I also talked with chix about the Indra incarnation from FC and decided against it for GD (Though Indra's chakra is still particularly strong within him, he's just not indra's incarnation, as it doesn't really grant him anything and it'd be more work having it from story purposes. That's my input :3