Found this:
“Saw a commentor on the front page saying that R2 and C3PO didn’t need to be in the prequels. But iirc, Lucas was influenced by Kurosawa’s Hidden Fortress, which saw big events from the point of view of 2 slaves, or in this case, droids, insignificant to be noticed, but clever enough to record the historical events as it happens.”
Cool stuff. Thanks!