I'd argue that it's because even though blocking IO is cheaper, it's very difficult to maximise performance in a multithreaded/concurrent context. You could ma

I'd argue that it's because even though blocking IO is cheaper, it's very difficult to maximise performance in a multithreaded/concurrent context. You could make faster code with it but I wouldn't want to maintain it and you'd have to throw an obscene amount of man hours at it to get that performance.