For general reference,
Multicameras in cockpit
Frankfurt - Los Angeles Boeing 747 Cockpit View [HD] - YouTube
View of instruments only
FIRST OFFICER IN ACTION! (APPROACH SBEG) - YouTube
Pilot view landing in poor weather.
Bad Weather Landing Brussels Cockpit B737-500 - YouTube
To them, a cockpit video could answer some questions, and that is useful (far more than what you suggest, Sir, in the case of an accident investigation).
I was inferring they were useful to view other parts of the aircraft, ie cargo and engines, as mentioned in an earlier post.