Huh? That's what I'm wondering. Why should something like this go untreated? It's at about the same level as other things like depression and schizophrenia in terms of "incredibly difficult to do anything about."
Because there's no issue with the person having it, only with people around them not being able to accept it. They could lead a perfectly happy life with the illness if their environment cooperated. Depressed people can be annoying because they get you down, schizophrenics can be annoying because you can't trust them to be the same person as last time, but there's literally nothing that can annoy someone that a transgender does that isn't making you question their own loveuality (this is assuming none of those blatant attention seekers, where transgenderism is just a manifestation of a different, attention-seeking mental illness). They're still in a mental state you're familiar with (assuming you've met at least 1 man and 1 women before), just in a different exterior.