Thanks for all the great discussion. I guess to clarify I would give an example of a photographer in a medium sized town (25,000) around WW2. Could be in England, the US or Germany. A big part of his bread and butter would have been making portraits of servicemen, after enlistment, before shipping out, back on leave etc. For the families of a good number of these GIs this may be the last current memory they will ever have of their loved one. If the soldier survived the war, it becomes a memory of an event that no doubt changed him forever.
Of course there are also the wedding photos, school pictures, business photos etc. The sort of stuff that would be very run of the mill for any studio photographer. Yet these run of the mill photos contain so much value for those who cherish the memories they hold. I can honestly say that if offered a trade for an early print of my favorite Strand or Weston for the family photos I mentioned I would decline.
I guess I am always in awe of the power of photography as our link to the past and that what are considered obligatory images when made become true treasures down the road.