Well, a good part of it is because in general LGBT stories are made/tailored for those people.
For example, I looked at your novel Dragoneth, I feel like the hook of the novel gay incest, which many people find morally wrong.
While, I do not have an issue with consented incest, I would not read your story because you made it a plot point rather than something in the novel.
It was not the story of two brothers who did blah blah, which is why I would pass right away.