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I might be misunderstanding the old school original situation, but your modern setup does not enforce/encourage that the door is closed. Even an automatic closing mechanism could be blocked by something.

With the Berlin key if you want to get your key (ostensibly you do and certainly don't want someone else to take it) you have to close the door. Of course you can still leave it propped open but unlike in your modern setup you actually have some stake in making sure it is closed.