Why would you take perfectly good code that works across many browsers and force breaking changes onto existing NodeJS/Browsers? WebRTC Condit, STUN, TURN, etc. do not require advanced language features.
Most, if not all, ES6 features are supported where WebRTC is supported, and it has great benefits for both users and developers. async/await and other ES7 have been supported for 14 versions of chrome now, but that change will come later this year, so we'll be supporting 95%+ of the market. Anyone can always use webtorrent as a module and transpile it.