Many hypothetical questions contain the condition that there is no consequence for your actions in the given situation. This is because this condition brings out the real morals of a person out of the context of societal judgement that would lead to consequences that would outweigh any other answer to a hypothetical that is not accepted by society. Thus the simple existence of these hypothetical questions shows that many humans wish they could operate in society without the consequences of society. In Jekyll and Hyde the main character shows a desire to operate in a similar fashion due to his actions in the book. By trying to separate his being into a good and evil it shows that he still wanted to be able to participate in actions frowned upon by society and yet somehow bypass the societal consequences. So in many ways what Jekyll did was something that a lot of people want which is to able to operate outside of the pressure of consequences in some way.
In a similar fashion there are many serial killers that operated almost in the same way that Jekyll did. There are many cases of serial killer that managed to maintain a seemingly normal life while also murdering people in their free time. In a way they also switched identities at will to still protect their normal lives so they could act upon their instincts that cannot exist in a civilized society. In other words Jekyll acted upon very human impulse that many people would not pass on.
