IMO it's a beautiful abstraction. You don't need to think about threads, just that your code will continue later when the result is available. In threaded environments like .net you can also create a CPU bound task that will be run in the background, yes in a thread pool, but you don't really need to know the specifics, it's something that you create, release the current thread (e.g. UI thread). For some IO tasks there's no even a waiting thread, so in that case thread would be the wrong abstraction.