A script is just another command, the only difference in this case is that you wrote it and not someone else. If its purpose is to make changes, and it's obvious what changes it should make without any arguments, I'd say it can do so without further ado. poweroff doesn't ask me what I want to do - I already told it by executing it - and that's a pretty drastic change.

Commands that halt halfway through and expect user confirmation should definitely have an option to skip that behavior. I want to be able to use anything in a script of my own.