Why is the literature of exploration filled with so many journals letter band other nonfiction sources?

The literature of exploration is filled with journals, letters, and other nonfiction sources because they provide firsthand accounts of the explorers' experiences and discoveries. These primary sources offer insight into the challenges, triumphs, and hardships faced during expeditions, making them valuable historical records. Additionally, the personal narratives in these sources often convey the emotions and thoughts of the explorers, adding depth and humanity to the stories of exploration.