In the case of Hello, the goal is to provide a fully FOSS video chat client built entirely on top of HTML5 APIs. That's huge! Skype, Hangouts, Facetime, etc. are all proprietary. Firefox Hello doesn't even require anyone to sign up for an account!
With Firefox Hello, I could paste a link in this comment that any reader with a WebRTC-enabled browser could click on and start a video chat with me. They don't even need to be using Firefox - they could be using Chrome on the laptop, or even Firefox for Android[0].
People keep bringing up the Telefonica branding, but that's kind of a red herring. Basically, since not all devices have globally addressable IP addresses (yet), they can't have it be fully P2P (yet), and they need some server that can facilitate the initial connection. Telefonica sponsors these servers, so they get their name listed alongside Hello.
What would "stripping out" Firefox Hello provide? It's built entirely on top of HTML5 APIs (which is why it works in all browsers with WebRTC support), so it doesn't actually increase the browser surface area at all.
[0] Yes, I can use my phone's FOSS web browser to place a video chat using a FOSS web client. If that doesn't sound amazing, I don't know what is!