The authors do this because a genre is a way of presenting an idea and it can make difference by itself.
Explanation:
The concept that the author may want to tell or explore will often take very different forms in different genres due to the simple nature of the genre itself.
The genre that is being used dictates how the theme will be treated so a writer can explore the same thing with different perspectives using different genres.
Each of these times they can do changed to the work that are to be reaffirmed in the final work and their oeuvre will reflect it.
