In my opinion, there are many reasons. Let’s see them step by step.
First, I think oversensitive people are less enjoyable to be around. Just imagine being around someone who has strong mood swings, who cries for nothing and hates you because you don’t agree with his/her opinion. It’s like speaking to a child.
Then, psychopaths don’t really feel emotions and are able to take more risks. They don’t fear easily, which is something valuable in society. Humans wants to be free, do whatever they want. Psychopaths are more free than normal people. They are not restrained by moral rules.
Psychopaths are more often intelligent individuals. They are often Bankers, Doctors and so on. Intelligence is a virtue seen in many leaders and entrepreneur. Intelligence usually brings to money, and money brings power.
So intelligence, risk-taking and fearlessness can bring charisma. This is why so many people are obsessed with the joker. He does whatever he wants, when he wants, and does not easily get caught due to his intelligence, quick-thinking improvisation skills and the danger he put himself in.
Interest is the feeling of wanting to give your attention to something or of wanting, to be involved with and to discover more about something. You don’t want to give your attention to something you find pitiful. If you don’t like mathematics you won’t make a bachelor or a master about mathematics. And we are educated to control our emotions. From childhood we are told to stay calm, don’t be violent, don’t cry in public… And in the end what better way to not show your emotions than don’t having any?