Does it help "the cause" by venturing out, of course it helps, the more people see a trangender person the more normal it starts to become. Now to answer the actual question "Is it essential"', no I don't think it is. There are many ways to help and they don't require someone to be out or even to be transgender. It is just as important for people to be supportive of transgender people and to let others see that it is ok to interact with us as they would any other "normal" person, none of which requires someone to come out..
