to tell the story in a voice of one of the characters
to enable the character to share thoughts with the reader directly
the person how has to write about the character is either the nararator or the author
Absolutely not. The "I" of the story is a character created by an author; it is not the author.
Author
Adele is the first person to write and sing Rolling in the Deep.
King James was not the first person to write the Bible.
James Madison. I am not sure if it is the first person but he did write it.
I believe it's first person
Maya Angelou was the first black person to write poetry and got recognized.
the person who wrote the first book wanted to have some excitement in his or her life, it might also be true that it was events that actually happened to him or her, also he or she might have wanted to write one just for fun.
First person is a more intimate way to write. The reader gets directly into the narrator's head and sees all of his or her thoughts and feelings. You use first person if you want that sort of story instead of a more objective story.
LL