WebRTC enables many of these things on the browser. That is the point. So your "I don't need WebRTC because I use native apps" is basically just "I don't need the internet because I can go next door to talk to my neighbors".
Just because something doesn't have value for you does not suggest it does not have value, period.
Almost. I'd say my argument is "I don't care about an online egg retailer shipping from China, because using the local supermarket is better in every way."
And obviously, Skype and IRC use the internet, too. So what is the benefit to me - the user - of "Skype inside web browser" over "Skype separate of web browser"?
I understand that WebRTC makes "Skype inside web browser" possible, but it also makes a lot of less desirable behavior possible. So there is be a trade-off between the advantages and the risks from adding WebRTC.
Which benefit does WebRTC generate for the user?
I.e. why is it a good thing that web browsers added this?
That's just a matter of browser software. The Web platform should not suffer just because the browser is imperfect. You can write your perfect browser, fairly easily with the libraries available. I will try when I have some time.
Just because something doesn't have value for you does not suggest it does not have value, period.