The attraction of trans women to straight men is an odd, but super, interesting rabbit hole to dive into. Sexual interaction, in and of itself, to a trans woman doesn't inherently make a man gay. Trans women generally view themselves as women. They often live their lives as women. They prefer being referred to as women. So, what separates them from a biological woman? Testosterone and genitals, but seeing as the former often dissipates further into transition and the latter is an expensive and often dangerous surgery, many keep their biological genitals for some time or even their entire life.
Put that next to a woman who has, say, Vaginismus, for example. Which is the involuntary tightening of the vagina. This often makes natural sex difficult, if not impossible for women. So, you have a woman who can't sex vaginally and a biological male who identifies as a woman (who is obviously restricted to anal and oral.). What exactly separates them at that point? If the fucker views the fuckee as a woman, and the fuckee also views themself as a woman, then isn't that still straight?
You're fetishizing what amounts to someone essentially being born in the wrong body, which isn't going to make sense as it doesn't make sense in and of itself. Sure, you could argue that throwing a trans women into a game made for sex is still fetishizing (and it is.), but the dev often includes it because it's their taste - a taste that's far more common than most men would have you believe. That's not even getting into the whole 'shemale' side of things. So, again, trans content isn't inherently gay - as said character, if portrayed accurately, doesn't identify as a man. It's your view of trans women that makes it gay. That's not to say you're a homophobe or a bigot, you just aren't attracted to trans women. That's fine, you do you. Get off on whatever you get off of. But shoving trans and gay content (despite the irony of enjoying lesbian content.), especially given how psychologically rooted the former is, into the same pile is narrow-sighted.
As
Geralt_R said, it's often a choice (unless the game is built around Futanari, but that something different entirely) most games. While I tend to laugh at the word 'inclusion' and 'representation', as they're both demeaning and patronizing to those its being aimed at, there's nothing wrong with a dev including it if they enjoy it.