I think it would be useful to examine the whole idea of “writing” and writing well. When I used to teach my writing course for Computer Science majors, I began with this question: ‘How many of you have ever had a broken bone?” After the show of hands, I followed up with, “Does it still hurt?” followed by “How many have been deameaned by a teacher or other authority figure publicly?” Just about everbody raises their hand. Finally, “Does it stil hurt when you recall that incident?” A good demonstration of the fact that Words have Power.
I end the discussion by noting that when you are interviewed for your first job, you will be judged first by the way you look and then by way you speak. (Actulally, your first impression will be on the way you smell, but I digress) To advance in your profession you will also be judged by the way you write. Rightly or wrongly, most people view the quality of your writing as a measure of intelligence. So in a very practical way, your writing skills are important.
In the course we examine various technological situations that have ethical overtones and analyze them by writing about them. This forces you to be honest: when you talk you can fake it by repeating a phrase or inserting a bunch of ‘ya know”s and other copouts. You can back up and rexplain if you sense the other person is not getting it. Not so when you write; the reader should get it right the first time. This means that is your responsibility to write and rewrite until the writing is a clear as you can make it. So, another benefit or writing is that it CLARIFIES YOUR THINKING. This,I think, is the greatest benefit of writing --- and I find it to be a very useful problem-solving technique. When I have some difficult problem to solve, I can analyze it best by sitting right down and writing myself a letter (as the old song reccommends).
Of course, like most things in Life, writing can be good or bad. In my humble opinion, I believe that good writing is signified by three characteristics: it is clear, concise, and coherent.
You might add that writing must also be interesting and factually true and I would agree but add the caveat: being true is not quite enough if you want the thoughts within your writing to be received and understood. The Buddha has said our words must be both kind and true to be effective. Even if true, if your words are unkind, the reader will either reject or just not absorb them. Worse than preaching to the choir, you will be preaching to an uncooperative closed mind.