With so few volunteers these organizations can't be choosy. Not many people want the out and proud kind of life. Many start out being that way, but most change over the course of transition and just want to move on with life.
A better question would be why are they so few overall (gay or straight). For example are there any at the HRC at present?
it comes down to what and why the "T" was tacked on to the end of the Gay and Lesbian movement, and if you as a person want to be associated with those who lay claim to their definition of that Letter.
Personally, the more people try to push their definitions of whom or what I’m supposed to be the more I want to disassociate myself with them.
I’m in a relationship which is defined by my spouse and I, we do not lay claim to any one particular social definition of what our relationship is, be it lesbian, gay or heterosexual. I present myself in all respects as an adult woman, who is active within her community. through volunteer work and various organizations.
in addition, I have a medical history of being both intersexed and having been afflicted with gender dysphoria, that medical history is simply that, it doesn’t automatically mean that I have to abide by the rules of a group of people who choose create a sub community outside of the community that I live and work in on a daily bases.
this attitude is why you don’t see many heterosexual leaders within the Gay and Lesbian community, and that is regardless of the individuals gender identity.
Addendum:
I agree towards equal rights for all people, but do not like to be classified or categorized under the Transgender label, for me the best avenue I have is through education and my presentation to those I work with every day. The point being is that I don’t care if a person identifies my medical history; I try to correct any misgivings by presenting a respectable individual.
I also do not belong to the HBS camp.
I do however support some of the youth programs and the IFGE, the transgender law center along with a few different organizations that follow similar beliefs.
As to marriage equality, I personally feel that by allowing religious rites to dictate above the United States Constitution is literally spitting upon the graves of our fore fathers and those who’ve given or put their lives on the line so that we could debate about such issues.
HRC = Human Rights Cowards, Honestly in my opinion HRC is a very bigoted towards anyone who is outside of their scope of straight acting gay males. They in any number of instances used trans people as political cannon fodder for a while