They adopt this belief as the only truth without a single doubt that motherhood is woman's sacred duty and purpose in life. Those women become the fiercest defenders of patriarchal roles and bear children or dedicate their lives to taking care of other people's. Social norms which fully agree with religious ones in this regard, claim that motherhood and maternal instinct to bear children is normal and natural. Those women who do not feel that way and do not pursue to give birth, can not be considered as normal, as 'genuine women'. . Society is based on stereotypes.
Women have biological, anatomical possibility to bear children.
If she chooses to become a mother she is sure that she will be respected, at least in words for that fact alone. Therefore, most women fulfill that possibility in order to gain any kind of acknowledgement in the eyes of the society, but in their own eyes as well. It comes more naturally than to use any of other numerous possibilities women have been born with because for them they would need to invest far more energy and time without any guarantees that the result would bring them rewards of any kind. Children are not being born because of the maternal instinct. Only a very small number of children is being born because they have been planned, expected and consciously wanted by their parents.