To some degree its a style choice but most (all?) of the languages used for UI use some kind of the UI thread paradigm with a way to run code on and off of that thread. Not everything called a coroutine is designed for UI interaction. Kotlin's are better suited than Goroutines. As you admit your self, js and others have settled on this style and one has to assume its for a good reason.
Async/await solves the problem of posting execution to another thread, getting a result, and easily and efficiently waiting for that result on exactly the thread you need.
It'll be interesting when or if someone uses Loom in the UI space.
