"No man but a blockhead," Samuel Johnson famously observed, "ever wrote, except for money." This is tough news for poets, since the writing they do is often less immediately profitable than a second-grader's math homework (the kid gets a cookie or a hug; the poet gets a rejection letter from The Kenyon Review). Poetry itself is tremendously valuable, of course, but that value is often realized many years after a poem's composition, and sometimes long after the end of its author's life.
In the meantime, everyone has to eat.