It's also useful as documentation even in single-tasked programs, since async ends up as a "good-enough" IO monad. Then again, few programs are actually single

It's also useful as documentation even in single-tasked programs, since async ends up as a "good-enough" IO monad. Then again, few programs are actually single-tasked in practice, and libraries often end up taking advantage of those async primitives for doing stuff like connection pooling even if your application code doesn't see it.