Generally the brake system stores enough vacuum for three full presses. If you need anything close to that, your engine should be running.
Once you're moving, especially at driving (not parking lot) speeds, power steering doesn't add too much. Cars with electric steering have it come right back. I'd be concerned about whether an automatic transmission car would treat things like locking the column, but I can't really speak to that.
But shutting it off
does override the computer's desire to keep the revs up.
