
Because we’re not a “third gender”. Since sexualities are usually labeled based on the gender someone’s attracted to, it kinda doesn’t work if we aren’t exactly A Specific Gender. Like #1 said, many of us don’t want to be labeled or put into a box like “this is THE/A gender I am attracted to.” Also, there are traits GENERALLY (real emphasis on generally) associated with men and women, but “nonbinary” does not have a traditional look or appearance.