That it wasn't a "serious" encyclopedia, probably due to its low cost. Another comment mentioned being allowed to use Encyclopedia Britannica and no other encyc

That it wasn't a "serious" encyclopedia, probably due to its low cost. Another comment mentioned being allowed to use Encyclopedia Britannica and no other encyclopedia in school because it supposedly was the "most authoritative". It also was the most expensive while F&W was the cheapest (World Book was in between in cost).