I don't really understand why yet. At the same time, there are a lot of cultural assumptions about why someone might be CD/TG. I think it's very important for me be up-front and honest with myself about which of those assumptions might be correct. Possible motivations for wanting to be CD/TG include:

• escapism
  Some people have an urge to immerse themselves in a fantasy world, as a way to try to escape the realities of their daily life. Imagining one's body being transformed can certainly be an immersive fantasy.

  This is well-known, it's termed the "pink fog". One should certainly be aware that it can be escapist fantasy, but that doesn't mean one must avoid it completely.

• fetish
  Many transgender biomales report being aroused by the initial phase of wearing feminine clothing, but that the arousal goes away as the clothing becomes an everyday banal occurance.

  See the autogynephilia page — there isn't a difference between people who get aroused and people who are transgender.

• wanting what I don't have
  It could be suggested that I want boobs/etc, and during times that I don't have a girlfriend, getting boobs/etc of my own is a short-term stand-in for this desire.

  (even though I'm pansexual, this can still apply, since if autogynephilia applies for more masculine partners as well, I don't miss mascunline body parts as much, since I've already got those)

  This one ties in with the very negative dichotomy of transwomen into deceptive/pathetic, with this being the pathetic side. But that doesn't mean it's necessarily false.

• gender isn't innate, it's a performance
  I think people react badly to this suggestion, because the only thing holding the idea together is our collective agreement that it must be true. (I suppose people might react badly because it really isn't true, but I don't think so)
• attraction to androgyny
  I've been attracted to androgynous people for a while, and I'd like to be able to "out" myself as part of this group sometimes. (just as lesbians wear certain items of clothing to signal to other lesbians that they're in the club)
• being subversive
  I've always marched to the beat of my own drum, and identifying as queer has become a very important part of that.