Having tried it out, I'm more than a little puzzled. What I don't understand is why make this yet another new platform, instead of just adding it as a new feat

Having tried it out, I'm more than a little puzzled. What I don't understand is why make this yet another new platform, instead of just adding it as a new feature to hangouts? All they've done is introduce friction to the onboarding process. Unless I'm really missing something here. As the linked article says, Google already has our contacts, and they already have a list of the people we chat with, etc. Why not just make use of this instead of asking everyone to start from scratch again?