jworth...you said "...I would be more reliable than me." OK. I guess.
Okay, I agree with your immediate consequences point. So how about this one: Do you ever forget to take out the ignition key when you leave the bike? That is comparable to the petcock question.
Speak for yourself...I NEVER forget that, and I am trained to associate the key with the petcock. Other folks do what they do, but I was speaking for myself alone right from the beginning.
The same kind of debris that could cause the vacuum shutoff to leak could plug the overflow tubes. Then hydrolock! IT HAPPENED TO MY BIKE TWO MONTHS AGO!! The (new) manual shutoff really shuts it off! Oh, and I have the tubes too. But they are less than 100% reliable, by actual experience.