No, cross-compilers to JS are and were thing too, and were used by cryptominers.
I don't need WebRTC for chat, because IRC is still working just fine.
I don't need WebRTC for video calls, because Skype is still working just fine.
I don't need WebRTC and WebAssembly for online gaming, because I have Steam to install games locally. Plus latency and performance of games emscripten-ed to wasm tends to be atrocious.
So the only uses where I have seen the new Web* APIs in my life was obnoxious ads and newspaper websites trying to shove recommendations and notifications into my face.
What would you want to cross-compile that couldn't be done much better by building a proper local app?
Just because something doesn't have value for you does not suggest it does not have value, period.
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?
Chrome OS was far ahead of its time, both in its general user hostility and in its excessive resource consumption for seemingly mundane tasks. Like when your roommate's YouTube streaming makes your Excel-like app horribly slow, because your new spreadsheet app needs high-speed internet for no obvious reason.
BTW, WebRTC and WebAssembly were great for crypto mining trojans embedded into ads. Before, they had to port their crypto miner to JavaScript by hand. By now, you can just cross-compile it. The progress of technology ... helps only the technology, but not you, the disposable user in front of the screen :p