I guess the authors understand that "localhost" is not an ideal authentication mechanism, however, the fact is that many application do use it as such. And the

I guess the authors understand that "localhost" is not an ideal authentication mechanism, however, the fact is that many application do use it as such. And the reason why they decided to come up with the RFC, to at least fix this on the level of DNS resolvers. (And I am not sure this thinking will ever be dead, it's kind of extension of notion of "territory" for physical objects, and you can still pretty safely assume that whatever is in my home is my own.)