When I look at historical cases, it seems different from a case today. If I’m a programmer in the 60s wanting async in my “low level language,” what I actually want is to make some of the highest level languages available at the time even more high level in their IO abstractions. As I understand it, C was a high-level language when it was invented, as opposed to assembly with macros. People wanting to add async were extending the state of the art for high level abstraction.

A language doing it today is doing it in the context of an ecosystem where even higher level languages exist and they have made the choice to target a lower level of abstraction.