Why does writing well matter?

Writing well is also a means of training your brain to think well, which can serve you throughout your life. Good writing forces us to think about the ideas and feelings we wish to communicate to others, and in the act of setting these down, our brains are organizing our thoughts, picking and choosing what is relevant and what is not, and exercising our mental muscles in a way that talking or just thinking does not. Writing is a purposeful act, and in meeting that purpose, we are forced to do a kind of mental work that strengthens the parts of our brain that help us solve problems, evaluate evidence, make decisions, and get along in the world. The kinds of essays students are assigned for writing bear this out. A process essay forces you to break down a process and understand how it works. A compare-and-contrast essay forces you to look at similarities and differences in an organized way, which is a template for decision making in many areas of life. A literary analysis forces you to consider the effect of the use of language carefully, a skill we all benefit from practice in. A persuasive essay forces you to consider the elements of persuasion, so you can consider not only how to persuade others, but also so you can see how others persuade you. An argumentative essay requires you to think about what is good evidence and what is or is not logical. Creative writing teaches you how to entertain with purpose. Who would not want to know how to do that better? Good writing reflects good thinking, and that is a skill worth having.

Writing well is very important to anyone. First, people judge you by how well you write. Your education shows through your ability to craft a sentence well and your word choice. Also, the tone of a sentence can change even though the literal meaning can stay the same. For example, look at these two sentences below:
"Tim carved the turkey."
"Tim hacked the turkey."  
Literally, they are the same—Tim is using a knife on a turkey. The words "carved" and "hacked" have different connotative meanings, however; the former is associated with a more pleasant mental image, while the latter seems violent.  
Writing well is also important for clarity. The best writers always keep their target audiences in mind and never lose sight of their purpose, whether it is to inform, persuade, or entertain. After reading a piece of good writing, you should be able to tell exactly how the author feels about the subject.
Good writing should not be limited to syntax and grammar, however; good writing also means using punctuation properly in order to make the sentences easier to read. All of these skills take time and practice to learn and use well, but good writing is a skill you can take with you into any job.