My guess for so many is because its virtually impossible to have ONLY ten top favorites of Dukes movies. My lists change depending on how I feel. However, movies like: Stagecoash, Fort Apache, Rio Grande, Hondo, Allegheny Uprising, Sands of Iwo Jima, Rio Lobo, Big Jake, The Searchers end etc--will always be in at least my top 15 most favorites.
So it'd be much easier just to do a top 15 then. 
