Because gays weren't as socially accepted ten years back. Back then they were burgeoning between the bubbling of 'tolerated' in the 90s to 'quietly accepted and tolerated' in the 00s and have come to a point where gays are in that area where they are fighting to be seen as equal human beings. As such, they want to be in more media than a campy lisping gay joke. Things like Ellie from The Last of Us or Arcade and Veronica from New Vegas. I think it's a good thing to give a positive depiction of gays as normal people than saying "SEE THIS GUY/GIRL? SHE'S GAY! OOOOHHH!!!" and that's what a 'normal' gay character does. It breaks the mold by showing gay people aren't floating faeries that spew glitter and fashion snippy comments but living breathing men and women who are no different than their heterosixual counterparts.
That said however, my problem with this thread is the OP getting hyperoffended over nothing. It'd be like me getting mad I have to play as a gay woman in the Left Behind DLC of The Last of Us. Granted, the situation is a little different since an RPG character is usually more moldable like clay than a set in stone character. But my point here is the OP kind of sounds like they're just drumming up controversy for no real reason than to do so.
Edit @WTFflag:
Of course, but it's easier to reflect a black man than a gay man because all you need to do is apply a different skin tone. Defining a gay man isn't something so easy as what's on the eyes. It's a part of a person's being and it is probably just an overlooked thing that happened with the game in development but we literally know nothing about how the game works, so we have zero idea of how the game works in terms of how well we could roleplay an alternate sixuality, which falls into my above point of OP making mountains out of mole hills.