"In our campaign we met Conan. We killed him and took his stuff!"It's in order to keep these great heroes of story "magical" and "pure", untouched by the grubby coarseness of mortal stats.
I mean, just think how horrible it would be if your PCs actually met and killed one of these paragons of literature! *rollseyes* Obviously, these figures are too important to ever be equaled by the likes of mere PCs.