What is the Purpose of Writing?

Today in class we watched a speech made by an introvert. She talked about how society, as a whole, tries to squash the traits of introverts-being quiet, enjoying solitude, working best alone, etc. She then claimed that though extroverts are important and needed in society, they are not necessarily the best leaders. Being loud does not mean you should be in charge. I completely agree with her.
See, the thing that's so cool about introverts, extroverts, and ambiverts is that personality is 100% needed and 100% important in society. Fact is, having different personalities is great! It's awesome having all kinds of people, who love different things and enjoy different hobbies. No one personality is better than the other, and no one personality should be enforced and seen as the norm.
It seems like a silly thing to be annoyed that the personality of an introvert is boring and dull. But what's really wrong with being boring and dull? That's not the point, however; the point is that when a large percent of the world has one general set of traits, and those traits are seen as negative, it makes a person not want to be themselves. Yes, it's not an issue like racism or sexism, but many people feel badly because they were born with a certain personality. And that is an issue.
Maybe if introverts were allowed to be alone and they weren't discouraged, systems and ways to combat serious problems like racism and sexism would have been created. But no use wondering about what something could have been.
Anyway, Ms. Amodie then asked us if people write to argue, or to persuade. What was the purpose of the video? In this case, I would say that the purpose was to argue on the side of introverts. She didn't try to persuade people that introverts were better, she argued that being an introvert is natural and shouldn't be something people look down upon. She argued that introverts often are natural problem solvers and that many people we look up to-Rosa Parks and Gandhi, for example-identified as introverts. She also provided a counter argument: extroverts are needed because they help with teamwork and the spreading of ideas. But she did not persuade her audience to see extroverts as less helpful, she simply argued that introverts and extroverts are both needed in society and in the workplace.
But what about other writing? Is it's purpose solely to argue, or to persuade? I don't think any piece of writing has one sole purpose, even the speech we watched in class. All writers who argue use persuasion to prove a point, and people are better persuaded when presented with clear, concise arguments. And then there's fiction. Fiction doesn't necessarily argue or persuade readers. Some work does-it encourages readers to look at different ideas and analyze their beliefs. For example, Harry Potter is very anti-racism and Animal Farm clearly is used to show the problems of communism.
However, some writing is simply made to entertain. All writing has a purpose, but the purpose is not always to argue or persuade.