Why was it so important for Rukmani to have a son in "Nectar in a Sieve"?

In Indian culture, gender roles were strictly prescribed, especially in rural areas during the mid-1900s when the story took place.  A woman's role was to take care of the house, raise the children, cook, and oversee religious and cultural rites.  A man's role was to earn money to support the family.  Couples were expected to have children, and faced great stigma if they, for whatever reason, did not.  It was especially important for a woman to have sons because a son could be taught his father's trade and eventually assume responsibility for the family's financial well-being.  Daughters, on the other hand, were a double financial liability - traditionally, they could not earn money on their own, yet they would require a dowry from the family in order to eventually marry.

These standards still apply in many parts of India today.