Why is a woman's housework often not counted as real work?

1. The work women do within the home is not recognised as work. 2. It is assumed to come naturally to women, so it need not be paid for. 3. It is in fact time consuming and demanding, so the claims of little time or high wages fail. _Source: NCERT Class 7 Social and Political Life, Growing up as Boys and Girls, Valuing housework_