Too old, too ugly, too fat, too emaciated, too sick, too deformed, too timid, too mentally ill, too poor or abandoned or homeless to attract another. These are singles, too. As single as they can be.
Singles are more than the singles' scene.
I see them every day, around the blocks where I live. I see them in the elevator. They drop their cookies, spill their coffee. One was burned, long ago, all over his face. One has a good sense of humor, also a hole in his neck.