Why are some people introverts? For the very same reason that some people are extroverts. I would say, there is no why answer to this.
If you have realized that you are introverted, that being with yourself, being within yourself comes naturally to you, you are comfortable with it, it is absolutely fine.
There is nothing wrong in being an introvert. Rather it is wrong to be someone you are not. You are moving away from your very centre.
Yes, society tends to attach attention to folks who socialize/talk, apparently projecting the idea or belief that Extroverts/Talkers are Smart People. If these folks find someone silent, the first “advice” is why don’t you go and talk/socialize with someone.
Folks who talk too much, also have this tendency to blurt out stuff not really opportune at the moment. These folks also at times fail to understand the value of silence. And people do require silence.
Can you imagine someone socializing/talking 24 hours a day. Even these so called extroverts require their periods of silence. Only then the rest is complete. Introverts simply require extended periods of silence. So being introverted is being more than fine, nothing wrong with it at all.
Further, it isn’t a problem, so the question of finding a solution does not arise at all. You can fix only something that’s got a problem. But being introverted is your nature and not a problem at all. So be absolutely comfortable with who you are and accept yourself who you are.
There may be many ignorant ones who think and convey that “all should be extroverts” and there may be many ignorant authors who may have brought out books in this topic. Such folks are best left ignored.
The problem arises if “being introverted is considered unacceptable” by individuals due to social norms and expectations. Then a problem has arisen!! If however an individual accepts that he is introverted, and he is happy being that, where is the problem?? No solution is even required.
If I were to summarize the above, it would condense into “Start with Acceptance”, an acceptance of who you are. You simply cannot be anybody else… and peace descends of its own accord.