The most important questions, the existential ones, should not be left to the sloppiest and least able thinkers. Equally, careful and rigorous thinkers should not confine themselves to unworthy or merely preliminary topics.
For example, some of the best heads in philosophy work exclusively in the philosophy of science. But for a philosopher to be a a mere handmaiden of positive science is an unworthy use of his abilities. Better to be a handmaiden of theology. But best of all would be to be no handmaiden at all. Philosophy is ancillary to nothing, unless it be truth herself.