My high school art teacher told me once that she believed I probably had a great deal of talent, but that she would rather I discover a new source of inspiration.
The illustration that prompted this feedback was an exercise in pointillism - the method of creating a coherent image from a series of light and dark dots. I believed (and my teacher agreed) that I had perfectly rendered the subject of my drawing, and that, by using only dots, I had created a mood and tone that impacted the viewer in a way an ordinary photograph of the object might not.
Where we disagreed was in the appropriateness of my choice of object to be rendered. My subject: a human skull. With a mohawk.
Needless to say, as a teenager, I was a touch obsessed with the occult. I listened to heavy metal music, studied demonology and played videogames. Did this make me abnormal? Hardly, despite what my art teacher may have thought (I got a D on the pointillism assignment). Many of my peers harbored similar obsessions, and one guy I knew took it many steps further, wearing all black, with spikes and refusing to answer to any other name than "Beelzebub."
Granted, my friends and I attended school with students who were not interested in demonology, wore decent clothes in pleasing pastel hues and attended PTA-approved after-school functions, but those were the mainstream kids. We were the yang to their yin, the counter to their culture. A fascination with the occult has been a common side effect of interest in the counter-culture since the dawn of the counter-culture (which dates to approximately the dawn of culture itself).
The most well-known association of demons with counter-culture in the 20th century is perhaps the heavy inclusion of Satanic imagery and lyrics in heavy metal music, but popular musical icons have been linked to occultism since bluesman Robert Johnson supposedly sold his soul to the devil in exchange for sublime skill with a guitar. The origination of the ideal of this kind of Faustian bargain dates back well before man invented the electric guitar to ... well, Faust, the protagonist of a 16th century German folktale which itself was inspired by tales much, much older.
In the German tale (later immortalized for English-speaking theatrical audiences by Christopher Marlowe), Faust is an intelligent, but unsuccessful man who is dissatisfied with life and makes a deal with the devil to grant him extraordinary powers and access to the Earthly pleasures he has been denied. The devil grants him the personal use of a demon, who assists Faust in acquiring his heart's desires (including the sexual favors of a young woman), but the price is Faust's immortal soul.
The lesson of the Faust tale is traditionally that one must temper one's desires or else be tempted by Lucifer into selling one's immortal soul for a few nights of pleasure, which, as it turns out, is a pretty bad bargain. To say this tale serves mainly as a reinforcement of traditional Biblical teachings promoting Jesus-approved moral values would be an understatement, but why these particular tales endure when so many other parables do not again raises the question of why we poor humans are so fascinated with the occult.
To answer this question, I submit as one theory that being bad is more fun than being good. Not only do bad guys get the girls, but they get the cool clothes (see: leather jackets and Death's Head emblems), the cool powers (see: Force choke) and typically rock and roll all night and party every day. Granted, having one's soul set aflame for all eternity is a pretty harsh side-effect of having an awesome existence on Earth, but the concept of an afterlife is a pretty hard concept to wrap one's head around, even for believers. The negative effects of living a life of Earthly pleasure require imagination and faith. The positive effects are in front of us every day, tempting us with their awesomeness.
Why, then, are we fascinated with demons? Because even the best of us want a taste of how the other half lives. If presented with the opportunity, I doubt many people would actually take the "eternal damnation in exchange for a sexy, hot babe" deal, but in the same way that one has a hard time looking away from a train wreck about to happen, it's almost impossible to quell curiosity about the embodiment of the temptations of man.