Many writers distrust fiction that smacks of autobiography. They believe that autobiographical fiction represents in some way a failure of the writer's imagination, or that such writers have only one good book in them and, after they have finished their autobiographical effort, they will have spent their creativity and no more will be heard from them. There's an air of smugness in that kind of attitude. The writer who makes such a claim is, in effect, saying "Autobiographical writing is not real writing," and "I'm a real writer and people who want to be real writers should write like me--that is, from the unlimited stores of my superior imagination."
There might be some truth in the fact that writers whose first novels are autobiographical find it more difficult than other writers to write a second novel, but writers of any stripe have a difficult time following a first novel. I've heard that as many as half of all first novelists never write a second.
Robin Hemley, Turning Life Into Fiction, 2006