You make an excellent point here!
I think you're exactly right about that struggle with the added complexity inherent to being a person of a particular minority in difficult situations. That struggle, while an authentic part of queer life, is what the author could often choose to focus on, rather than a potentially successful romance?
I think the other wrinkle here is that queer representation in literature is often in the YA genre, so even hetero relationships are often fraught with teen angst, hemmed in with peer pressure and doomed to failure by the end of the story, let alone queer ones!
Fingers crossed more queer literature can cover all the different genres to more fully represent all of humanity.