If everything in Twilight is formulated to get the attention of the teenaged girl with vampires=sex thrown in and the right marketing there was no way it couldn't fail. My sister fell hard for it and the Percy Jackson stuff thinking it's the be all and end all because she has limited reading and educational experiences.
I can agree with the modern vampire standing for sex in modern media, the more stuff is censored the more people want to find a way to subvert and rebel. A guy who is waiting forever just for you is a common enough trope. Watching someone sleep can show up a lot too. Combining all that with some more unsettling stuff is wandering in to creepy territory.