[klabb3]

Imo this is because threads is a good abstraction. Not perfect, and quite inflexible, but powerful and simple. I would argue green threads are equally simple, too.

Async is implemented differently in different languages. Eg in JS it’s a decent lightweight sugar over callbacks, ie you can pretty much “manually” lower your code from async => promises => callbacks. It also helps that JS is single threaded.

Doing the same in Rust would require you to implement your own scheduler/runtime, and self-referencing “stackless” state machines. It’s orders of magnitude more complex.