That's the thing though, it's possible but it makes the simple hello world example more tedious. It's totally possible to make an abstraction layer, provide a tokio implementation out of the box but leave the door open for other implementations to slot in. Anyone who's written portable code for non posix systems is used to this experience. Standardization is definitely better but it also has its own share problems as it can limit what's possible. I expect that the decision to delay standardizing on these interfaces too early will end up leading to a better long term design. Especially if major improvements to async are on the horizon and can alter the final shape of that standard.