[robmccoll]

In single threaded scripting languages, it has arisen as a way to allow overlapping computation with communication without having to introduce multi threading and dealing with the fact that memory management and existing code in the language aren't thread-safe. In other languages it seems to be used as a away to achieve green threading with an opt-in runtime written as a library within the language rather than doing something like Go where the language and built-in runtime manage scheduling go routines onto OS threads. Personally I like Go's approach. Async / await seems like achieving a similar thing with way more complexity. Most of the time I want an emulation of synchronous behavior. I'd rather be explicit around when I want something to go run on it's own.

[fmajid]

Agreed. Async I/O is something where letting the runtime keep track of it for you doesn't incur any more overhead, unlike garbage collection, and that makes for a much more natural programming pseudo-synchronous.