Sometimes I write about the conflict inside me. When I do, it's because I hope to relieve some of the emotional pressure build up it causes. That is writing nobody else sees.
Other times, I write with an aim to move the people who read my material. I want to move them to act for a better world, a better future, a better life. That writing may be fiction or deeply researched factual material. Either can be used to convey ideas and motivations.
And either way, the simple, physical action of writing feels good to me. Whether by pen or keyboard, it feels good.