Hmm... How exactly do you know that? I can only think of a handful of full Flash sites I ever used, and of those, I learned of them from word-of-mouth advertising, not through a search engine. (e.g. Homestar Runner). There could have been tons of relevant sites locked up in Flash navigation (back when that was fad) that I never found out about because of their poor SEO -- the world would look the same to me whether they existed or not...