The WDYTYA producers seem to have a fixation with WW1 and WW2. I know we've been remembering the beginning of WW1 and the "real" end of WW2 (my dad was one of the forgotten army in Burma), but is every celeb only interested in their family member's war time experiences?
I wonder if that there might be a couple of reasons for that Lizzie -:
Every family would have been touched by events related to the war so there will be a war story for each of the celebrities even if nothing else of interest can be found in their family history.
There is a fair amount of information about the events and people who participated in wars so a cheap and easy way to pad out a programme. You don't have to dig very deep to find the required documentation.
There are many interesting, heroic and tragic stories related to wars - everyone had a tale to tell, so a constant supply is available. This also brings in an element of pathos, and the possibility that the celeb might tear up providing a good opportunity for a close-up.
PS. My father in law was also one of the forgotten army in Burma.