They are introverts
It is not like introverts cannot talk with strangers, but they don’t want to talk with people they do not know much about. Whereas extroverts are just the opposite, they love talking with strangers and are totally comfortable initiating an engaging conversation with them.
They are self-inhibited
People who are self-inhibited often restrain themselves from talking to others. It could be because of their lack of self-confidence, inferiority complex, or shy behaviour.
They are anti-social
Some people also do not like social gatherings, and hence, they avoid going to events where a large group of people would see each other. Anti-Social people usually do not like to meet new people; they feel comfortable with their limited group of friends and relatives.
They are afraid to speak
Some people are afraid that what if they speak about something wrong with strangers. This holds them back against talking in the presence of strangers, so they prefer to avoid talking. (See how can a man tell if they have high testosterone)
They lack confidence
People who have self-confidence issues often hesitate to talk in front of others.
They don’t share the same interests
If a conversation has already been built up regarding something that does not intrigue you or maybe you have not heard regarding that subject, in those cases, people prefer not to talk. On the contrary, you would have a lot to say in others’ presence if you find something to say within your area of interest.
They don’t feel comfortable
Some people feel uncomfortable while talking to a stranger. As their feeling is like, what should I talk with them? So they talk less or very limited with them. (See What Causes an Inferiority Complex?)
They are perfectionists
One of the reasons is that those people who talk less are perfectionists, so they speak less. As they do not want anything to say unless they are sure that whatever they are going to speak will sound perfect or not.
Wavelength does not match
If a person is talking to another person and is not on the same wavelength, they won’t agree with each other. Because they do not share the same opinions and interests, they think it is better to avoid talking rather than starting any conflict/argument.
They are concerned about something
When something is going in the back of some people’s minds, or they are undergoing a major problem in their lives, this could be one reason they become less talkative.
They have high levels of testosterone
If a person is suffering from high testosterone, it can make a person talk less and become anti-social.