In some cultures, e.g. where there's no payoff to any education beyond bare litercy and enough arithmetic to run a roadside vegetable stand, it makes absoluete good sense for girls to marry young. For one thing, childbearing is at its safest in the teens --- child-raising, too --- when the young mother's health and energy are at their peak, before diabetes, hypertension, kidney failure and the dgenerative diseases of age set in.
I’m not sure this story is describing teen marriage.