An answer by Hemingway quoted by  Matt Mullenweg (founder of WordPress, among other things) is this:

I believe that basically you write for two people; yourself to try to make it absolutely perfect; or if not that then wonderful. Then you write for who you love whether she can read or write or not and whether she is alive or dead.

— Ernest Hemingway to Arthur Mizener, 1950 Selected Letters, p. 694.

I, too, do write for myself and her but as much or more for the rest of the world–who I want to share my thoughts, my life, my experiences and my philosophy with.