I think it depends on the kind of person you are. Clearly, it's possible to transition without therapy. Lots of people have. At the same time, the people who did did so because they were headstrong or because they couldn't find one/lack of funds. I think if you know yourself and are willing to accept responsibility for your actions, therapy may not be necessary. However, there are a lot of transgender people out there with serious comorbid issues who really really need therapy, and there are others who just get what they can from it. I don't see a therapist since I have no insurance, though this may change once I'm a full time Master's student in January. So, in short, some need it, some don't.