Even entertainment has merit. Writing that brings a smile to the reader's face or relieves him of his travails for a while is important. In more challenging times, reading to escape has been extremely beneficial to me personally, so I "get" that it can also help others.
Then there's the educational value of writing. When we read about other places, times and cultures, how people behave (or ought to), we are enriched by new understanding and gain useful tools for living. Both reading and writing have taught me many things, including how to better communicate.
Our writing can have spiritual benefits too. While we could simply journal our experiences, it's as we share our personal stories of what God is doing in our lives, how He is shaping, growing and transforming us, that others can be inspired. God is still at work, still active, still meeting people in personal ways. These stories help us know that we are not alone and bring much comfort on the faith life journey. I, for example, love reading conversion memoirs since they give me hope for unsaved family members and friends. God continues to bring people out of darkness into the light - praise His name!
Perhaps the first and best thing to do when I sit down to write is to ask, "What is the primary purpose of this piece? Is it to entertain, educate, inspire? What does God want me to do/write about?" And then listen, actually listen, before pressing the first key or putting pen to paper.
My reasons for writing may be varied, but ultimately should have three goals: one, to meet a perceived need, whether it's entertainment, education or inspiration; two, to flow from what God is laying on my heart; and three, to glorify Him. He, after all, is (or should be!) my everything.
Susan maintains a website and currently blogs infrequently at www.susan-barclay.blogspot.com