Why do sons get married?

A mother asks: "why do boys get married?"
Son replies: "so they have someone to look after them"
Mum replies: "No so that the family has someone to look after them"

Is it me or is there something wrong in all of those answers? Surely a boy gets married because he loves someone so much that he wants to spend the rest of his life with this girl...to be with her, look after each other, build their own family and life together and grow old together. Surely the looking after the family is a secondary reason ...that comes naturally through love received from the family.
So how has it become the only reason to get married?? What is a wife then? Just a housekeeper? someone who cooks, cleans and looks after the family? Surely there is more to it then just that!