So, as I sit watching a TV show called "The Batman" I realized that more people are inclined to become the Joker rather than the Batman. Most people, when confronted with a situation that they cannot control, feel helpless. This helplessness usually results in a violent reaction, this violent reaction results in a "adrenaline rush" that makes the person reacting feel powerful. Power is an alluring thing. People are also destructive by nature, (look at the kick most people get out of seeing something blow up in a movie) hence the desire to be in a overwhelming situation again, and the easiest way to do that is create the situation yourself. The Joker does the same thing, he wants to be able to have that rush of chemicals and the best way he can think of to do that is to make a situation in which he is overwhelmed and he has to "fight", either physically or mentally out of it. The Batman's emotions have dictated that he only "fight" against the ones that are causing chaos, although he maintains the original principle of getting a "rush" from the fight, exemplified in the smirk that he usually carries when he knows he has the bad guy beaten. This emotional tug of war is something that most people want to avoid, so they opt for the most destructive and least resistive path to the emotional high.
This opinion is mine, but I don't mind sharing. Laterz.