All of the responses provided are valid reasons for a writer to include their reasoning in a text. However, if I were to choose the most comprehensive reason, I would say:
"It helps the reader understand why certain information matters."
This reason encapsulates the importance of reasoning in guiding the reader through the text and connecting the evidence to the overall argument or message. It ensures that readers can grasp the significance of the information presented, making the writing more effective and impactful.