Most of the other uses are pointless.
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?