Discussed this on my company site last week. 757 only needs a 60-80lb pull to overide the damn lock anyhow.
Bring back big, fat, smelly flight engineers!!! Nobody gave them any crap!
Key exists in case the captain goes a little bit myocardial whilst the FO is having a "catering offload" in the little room behind the flightdeck. Remember that Beech 18 where the pilot was screwing his passenger in the cabin and the door slammed shut? How about that Aeroflot Airbus with the (unconfirmed) report of two kids at the controls?
Extra door between FD and cabin.