Why are many people so adoring of serial killers?

I'm not trying to be some sort of a hypocrite, I'm fascinated by serial killers as well, but it isn't like I glorify any of them. They're indeed fascinating, but their actions were truly sickening, yet there's some much paraphernalia involving them. In addition, there are even serial killer groupies, such as in the case of both Richard Ramirez and Ted Bundy (well to be fair, a lot of these groupies tend to be convinced that this particular is completely innocent and has therefore been wrongfully accused, but generally that's not the case...).