The decision to write in prose instead of poetry is made more by the readers than by writers. Almost no one is interested in reading narrative in verse.
The idea of avant-garde art is a very suspicious thing to me, the idea that poetry is new and it keeps being new the way Chevrolets every year are new.
The Language Poets are writing only about language itself. The Ashbery poets are writing only about poetry itself. That seems to me a kind of dead end.
The young people have MTV and rock and roll. Why would they go to read poetry? Poetry belongs to the Stone Age. It awakens in us perceptions that go back to those times.
When you have an idea for a story, you want those characters to reach as many people as you can. I think you normally think of prose as a way of doing that. It fits our time, the culture.
Young writers only take off when they find their subjects. Since almost everyone has a family and stories about family, that is often a place to start.