I'm not so sure it results in a vastly faster execution, at least on OSes which don't need half an hour to spawn a new process. So, yes, of course it was needed for Windows, because there creating a new process is so expensive that sometimes you've got to mortgage your house to do it.
I was going to cover this topic (the cost of starting/forking a process) in my original comment but decided it would be a bit tangential since I was able to make my point without it.
On Windows the cost of forking a process is high whereas on Unix/Linux it's low but on both platforms every application has a nontrivial startup time that will be significantly greater than a native call within an existing process.
