Biography means the stages of a persons life span for example we would not just randomly talk about them being in war we would need to talk about how they got there like you can not just be in calculus math you have to have algebra first we need to understand how they got there and there majors.
To show different stages of life as they move on with time for example you don’t turn 5 and then 27. It’s to organize the stages of life and dates and times. Because biographies are about a persons life and how they grew up or came to fame so putting it in chronological order would help organize the historical events of that persons life. I think but I could be wrong.
