Ken,
Since you seem to be struggling with the concept of an extra pair of trained pilot eyes in the jumpseat enhancing safety when they are available, let me give you a simple example from my past.
Many years ago back in 1991 , I was sitting in the jumpseat of an Ansett B727 for the descent and landing into Adelaide on a flight from Perth thanks to a Captain who was very happy to have a keen professional general aviation pilot sitting in his cockpit.
As we were on a right base leg for the landing into Adelaide on a nice VFR day, and getting very close to the finals turn, it was my eyes that spotted a Piper Chieftan at our 12oclock low , very close ahead against the ground clutter of the city when boththe Capt and the FO couldnt see it too save themselves ( it happens to us all).
My callout and ID of the traffic and the Captains flying got us safely behind him whereas the situation /spacing would have required a go around by us if the traffic had not been seen for another 10-15sec as we would have flown thru the final approach path and be too close to the traffic to follow at a safe distance down finals.
I'm sure dozens of pilots on here could tell similar jump seat stories.
