Window in aircraft door
On many commercial passenger aircraft, there is a small window in each door to the aircraft. In the event of a crash landing, one wants to be very careful not to open a door if there is a fire immediately outside.
I realise all the windows next to passenger seats gives plenty of visibility... but it seems strange that the person potentially opening the door (ie can be passenger, particularly if crew are injured) cannot see easily from the door itself but must go somewhere else first to look. This seems to go against human instinct, making it harder to check the safety of an emergency escape route as people, particularly if untrained for a scenario, often panic in emergencies instead of thinking rationally.
Is putting a sizeable window into aircraft doors just too difficult ? Or is there another reason ?