Is it that you have something you think people need to know? Is it that you want people to know how you feel and what you think? Do you want them to tell you that they understand, that they feel the same? Is it that you need affirmation, someone to tell you that your words or your ideas are interesting or skillful? Do you want people to laugh, or do you want people to think you're funny? Is it the act of writing, the release and expression, that gratifies, or is it the consumption of the writing that matters? Is it the writing or the reading? Is it the feedback? Is it just another way to say, "Here I am?"
Yes, it's exactly various mixtures of those and other things. It's not always the same.
Here's something I wrote a couple of days ago.
Hello, friends. How are you today?
Later. Love.