According to the author, why did chronological age become important?

because it creates an order

explanation:

some researchers suggest the use of chronological age as a marker for the timing of adulthood, whereas others suggest the transition to adulthood is better characterized by events or rites of passage such as graduation from school, starting a job, or having a family (neugarten and hagestead 1976).

now, unfortunately, i don't know what author you are talking about, but i hope this helps.

good luck :)

have a nice day !!

if you don't mind posting the paragraph so i could read it that would a lot. (;