I always wonder why people would think that every pre-war Ghoul would be a valuable source of pre-war knowledge. Sure they may be able to shed some light on pre-war American culture and history but what are the chances of coming across a pre-war ghoul who was some scientist who specialized in Physics? The frequency of finding a pre-war Ghoul is uncommon but finding a Ghoul who was an expert in a field that the Brotherhood was lacking in would be quite rare. Also, would even pre-war Ghouls even remember the minute details since it has been 200 years?