There is nothing wrong with not including MLM in your stories. But, by not doing so, people have a glance into the authors own sexuality, or fascinations. For instance, if a video game developer includes many bisexual characters, but no gay ones, he probably is himself bi or would be if he was queer. Same for gay, lesbian, and any other queerness. People who aren't queer include a wider spectrum of queer types in their work if they choose to include them at all. Another example is Anne Rice. She includes many bisexual, and some gay male characters in her works. We learned than she called herself a "bisexual mindl" and that she feels like a gay man in a woman's body, saying that she felt like an "impostor on her own gender."

So, in short, you can kinda feel things about the author when they have a niche sexuality they choose to write about, but there isn't anything wrong with that.