Fallout: New Vegas is an incredible game, and its factions are its best part. The New California Republic (NCR), Caesar's Legion, and the Securitrons of Mr House are omnipresent in the Mojave, and there's barely an NPC in the game that doesn't shine light on some new aspect of each one.
So many of New Vegas' interactions add texture to its factions because, well, that was the whole point. In a recent appearance on The Examined Game podcast, New Vegas director Josh Sawyer said that one of his and his team's key goals for the game was "to make sure that the people in the factions felt like they were humans that were their own people.