I don't know. I can see the attraction sometimes of a lack of codification, especially as a DM.
Sure, but that alone is insufficient to explain the phenomenon. There are games out there (FATE, for example) that work without codification so much more smoothly than any version of D&D has.
 
				 
 
		 
 
		 
 
		

 
 
		 
 
		 
 
		