Queer concepts and why they're seen as queer (I am bored):
Vampires: the very idea of being "strange" or "other" has been inherently connected with queerness since forever. Vampires are generally cast out from society and seen as vile beings by humans. Sound familiar? Especially the idea that vampires never chose to be vampires.
Pirates: pirates are generally people who have left regular society in order to be free. The idea that normality and being like other people is keeping you down just sounds like a queer experience. Freeing yourself from the shackles of normality in order to be different is a queer experience.
Cowboys (specifically Outlaws): again with being cast out from society and being seen as different or other. Also, men riding horses. What's stopping them from riding something el- okay I'll shut up. Anyway, criminals in general are seen as kind of queer (depending on the crime) since being gay used to be illegal.
These kinds of concepts lend themselves well to queer stories and are connected with all kinds of queer identities and even ND concepts. Something being seen as "forbidden" or something that's "not allowed" is generally connected with queerness. Forbidden love is a queer idea. None of this to say these concepts can never be hetero whatsoever, but they connect more with queer and ND audiences. The feeling of being separate from the rest of society and being seen as something negative when you're just trying to live your life.