As it explains quite clearly, this is "portable system calls". Lightweight indeed, it's the whole point! So if you ask this question, you might as well ask why

As it explains quite clearly, this is "portable system calls". Lightweight indeed, it's the whole point! So if you ask this question, you might as well ask why system calls are not more expansive in their capabilities. I think there's a reason, system calls are much simpler. They are building bricks. If you want to layer something complex on top, you're free to do so. About your suggestions, ACE's documentation is particularly bad. I wouldn't recommend it to anyone.