It is the fear of being rejected or past events that caused this in their way of life. An unsociable person is not bad, but I would say that seeing people, interacting with people is a very interesting and entertaining thing.
Unsociable people generally stand back and do not participate in exchanges in a conversation with more than 2–3 people. They probably have the impression of being considered useless for conversation.
I believe that being sociable and enjoying seeing others is a wonderful thing that life brings us. And you? What do you think?