The desire to write is the desire to communicate. Even if you're just keeping a journal which no one else will ever see, you are communicating your thoughts in order to be accurate and as precise as you can be with how you feel about things.
Most of us want to change the world. This is the human condition, I think. Sometimes we only want to change the views of one person, such as when we write them a personal letter. At other times we want a wider range of influence, so we jump onto Hubpages.
Yes, it is gratifying to get feedback from others who read, appreciate, and get something out of our writings. If it wasn't, we wouldn't do it.
My life would have been entirely different, I'm sure, I hadn't been reading what others write for the past sixty-odd years.