Introverts might be as interested in people like others, but because of their nature, it might seem like they are not interested in people. An introvert could be enjoying the company of others, but might seem like they are not that interested at the same time.
People who have underdeveloped social skills or who don't really know how to socialize might find social interactions a burden. In such a case, those people might avoid social interactions whenever possible. See why some people feel uncomfortable around strangers.
People who suffer from social anxiety are very likely to avoid others. In order to seem normal, many of them claim that they are not interested in others, while in fact they are just afraid to interact with them.
Some people develop false beliefs about others in order to keep themselves protected. A person might think that all people are bad and so give themselves an excuse to remain in their comfort zone.
Some people like to interact with others, but prefer to remain in their comfort zone because of their underdeveloped social skills or coping strategies.
People who have antisocial personality disorder usually deal with others in an aggressive way. Antisocial people don't care about others and usually don't respect their rights.
Very high levels of testosterone can promote aggression and make a person less talkative. Not all people with high testosterone levels are not interested in others, but that factor could add to the problem. See how can a man tell if they have high levels of testosterone.
Parents who neglect their children or even abuse them might raise children with impaired social skills. Those people might become unable to connect with others or interact with them properly.
Some people lose interest in others in order to protect themselves from rejection, being hurt and other emotionally taxing events that might happen as a result of social interactions. Those people might not be aware that this is the reason behind their lack of interest in others.
People who think that they are boring, uninteresting or unattractive might start avoiding others. Some of those people might then start to convince themselves that they are not interested in people in order to justify their own behavior.
People who were betrayed, cheated on or abused could start to develop general negative beliefs about others like all people are cheaters or dishonest. Such beliefs can motivate the person to avoid others whenever possible.
According to one study, people who remember bad events and obsess about them might be more likely to avoid risky encounters with people that could lead to the repetition of the same events. Those people might avoid others in order to keep themselves protected.
Some people have few friends that they trust. Those people might find it very hard to expand their circle or trust more people. Those people might thus avoid others and just keep their small circle.
Depression lowers motivation and makes the person less interested in others. During phases of severe depression, a person might lose social interest and prefer to isolate themselves. See why do people get depressed.