Hello is just a thin wrapper around WebRTC. That's why Chrome can receive Hello calls without an extension. There's barely anything to add on in that case.
Is there a cost to adding even a button? Yes. But that has to be weighed against the benefit. And a significant amount of users benefit from having the button.
"Just one button" led to Netscape 6 and subsequently Firefox in the first place. It's easy to miss the significant amount of user benefit from not having that one button, since it's a smaller amount of benefit per person across a lager number of users.
That's a fair point and I agree, there is benefit to not having more buttons on the UI. It's hard to know what the right tradeoff is, between the benefits of adding buttons and not adding them. There are good reasons to prefer both more and less.
In this case, data on user behavior indicated that it was worth adding the buttons. It's still possible that the data is imperfect somehow and a more optimal tradeoff could have been chosen. Still, I think there is good reason to believe the current data and decisions make sense.
WebRTC is now a web standard and ships in multiple browsers. If you consider such technology to be outside the scope of a browser, then you're going to need to convince a whole lot of people.
The complaint is not about WebRTC, but about Hello.
The comments in this thread are going in loops.
"Hello shouldn't be bundled with a browser."
"But it is just a small wrapper around WebRTC."
"Yeah, but it's out of scope for the browser."
"WebRTC is a web-standard"
Mozilla's mission is to promote openness, innovation & opportunity on the Web. There's nothing specific about browsers in the mission, though it is used to help further the mission.
If you take that into context when you look at Hello, you can see why the organization might want to leverage the Firefox user base to introduce something with negligible overhead (Hello) that would help to advance that mission.
