Consider these facts:
When discussing another scholar’s research record, it is common to not give full credit for essays in edited volumes. Some people disregard book chapters entirely when assessing a CV. But it is more common to give a kind of discounted credit, counting a chapter in an edited volume as less than a journal article. Mindful of this, some people list journal articles and book chapters under separate headings in their CV.
When discussing their own productivity, philosophers are quick to mention collections that they have edited. It is common, on a CV, to see edited volumes under the heading of books alongside monographs. Even though philosophy is no longer a book-driven discipline, a monograph carries more weight than a journal article. So putting the edited volume under the heading of books puts it where important things go.
The puzzle is how assembling an edited volume can be prestigious and important work if the chapters assembled in them are insignificant. If it is not quite a paradox, it is at least a tension our professional norms.