Ref the Helios accident,
IIRC cabin crew and a passenger were observed in the flight deck attempting to revive the pilots using the pilots oxygen masks. They were unsuccessful as they were unaware the flight crew oxygen was switched off due to poor pre flight checks. The door was not a factor.
Ref the Turkish Schiphol accident,
Regrettably the flight crew were killed by the nosewheel entering the flight deck on impact.
All commercial jets have doors that deenergise with loss of ac power, have (simple) normal and emergency access codes, automatically unlock with depressurisation and an alternative escape path. It's just a question of where the biggest threat to the safety of the a/c lies.
I dislike locking the door but right now aircraft are safer that way, if a little less sociable.
Don't get me started on not being allowed to have my wife on a flight deck jumpseat though........
