Why were The Dark Knight Returns, Watchmen, and Maus originally serialized before appearing as books?

The works The Dark Knight Returns, Watchmen, and Maus were originally serialized in comic or magazine form because they were produced within the existing structures of the comics industry, which traditionally relied on the publication of monthly, pamphlet-like serial periodicals.1

While these titles are now celebrated as foundational examples of the graphic novel, their initial release as serials was standard practice for the medium at the time. The subsequent collection of these stories into book form was a later development that helped distinguish them from mainstream comics, which were often unfairly dismissed as being intended only for children.1

It is important to recognize that the term "graphic novel" has sometimes been used to enforce a hierarchy that denigrates the medium of comics based solely on format. In reality, these works were defined by their formal control, artistic innovation, and literary quality, rather than by the fact that they were eventually published as books.1