When people watch anime, they don't just watch it, they immerse themselves in it. They become obsessed, and it becomes a major part of their lives. It has a huge fan base, and incorporates fantasy, sci-fi, fetish, and realistic elements.
So when people get into anime, it's a no brainer that they'd get into it sexually. There are a LOT of sexual elements in anime shows. From school girl outfits to kinky sex, anime characters GET IT. But besides the traditionally sexy stuff, a lot of anime shows sexualize things that aren't traditionally sexy.
People get turned on by teeth brushing, magical devices, incest, and more weird things. I guess you can't really knock it till you watch it, right?
It sounds totally weird/f*cked up to people that don't watch anime, but it seems like most viewers get turned on by strange things. So perhaps they make that stuff look unbelievably sexy? BRB gonna watch some anime and see how I feel in mah private parts.