At least with old fashioned keys you can't easily give out a duplicate. I was once in bed, late at night, lights out, when someone let themselves into my room -

At least with old fashioned keys you can't easily give out a duplicate. I was once in bed, late at night, lights out, when someone let themselves into my room - a rather drunk guy demanding to know what I was doing in his room. The desk clerk had got his room number wrong and given him another card to mine. It all worked out OK, but under other circumstances I could imagine that it might not.