Board Thread:Theories & Speculation/@comment-1512913-20141028151348/@comment-2120712-20141030033800

That is because their techs are hiden jutsu. Meaning that the techs are not based on bloodlines, just that the teaching and usage of such techs are kept with the user or family. What it means is that if they decide to, the nara could start teaching non-naras the techs.