Curiosity?  The chance to engage in a fantasy that you wouldn't in the "civvie" world?  There's obviously a market for TS providers, and it's highly doubtful that they're making any money off homosexuals, as they'd very likely see male providers, not TS girls.

Is seeing a TS girl the first step on the "slippery slope to gayhood"?  Some of the Extremely Manly Men(tm) here would probably say so, but as far as I'm concerned, I seriously doubt it.  I'd wager that most guys who see TS girls are still very much attracted to women, but want to explore something that's "forbidden"... and what better way to do that than with a girl who looks like a woman but has that "little something extra"?

How do I figure this?  Because I've seen both TS and genetic girls, and enjoy each in their own way.  The TS girls I choose to see all have one thing in common (no, not that; well, yes, that, but that's not what I'm talking about): they all look, sound, and act very feminine.  If a TS looked like "a guy in a wig," I wouldn't see her, because I'm not attracted to guys (which is also why I don't see transvestites or cross-dressers).  All of the TS girls I've seen also know that they're catering to the crowd looking to experience "forbidden fruit"; they have no illusions otherwise, and are perfectly happy with it.

Like I said, there's a market, and they're catering to it.  Seeing a TS is no different than seeing a provider that's into all sorts of "offbeat" sexual practices (S&M, water sports, etc.): it's all about what gets your kink on.  And anyone who thinks that seeing a TS is the first step in coming out of the closet is, in my not-even-close-to-being-humble opinion, ignorant in the extreme.  You say you aren't sure, and I accept that (and I appreciate your honesty), but there are others who DO think that way... and to paraphrase you, "in their hearts, they know who they are."