Margaret Atwood asks why writers write in Negotiating with the Dead: A Writer on Writing (2002), sourced here.

These are the three questions most often posed to writers, both by readers and by themselves: Who are you writing for? Why do you do it? Where does it come from? …

Here then is the list:

… To pass the time, even though it would have passed anyway. Graphomania. Compulsive logorrhea. Because I was driven to it by some force outside my control. Because I was possessed. Because an angel dictated to me. Because I fell into the embrace of the Muse. Because I got pregnant by the Muse and needed to give birth to a book …

And ‘to pass the time’ reminds us of Borges who notes:

“I do not write for a select minority, which means nothing to me, nor for that adulated platonic entity known as ‘The Masses’. Both abstractions, so dear to the demagogue, I disbelieve in. I write for myself and for my friends, and I write to ease the passing of time.” — Introduction to The Book of Sand