Mainly two things:An Indian woman is expected to bring a considerable dowry with her into marriage, making it very expensive for a family with several daughters to get them all married.An indian woman getting married is (traditionally) pretty much expected to LEAVE her family behind, and "join" her husband's family. With a weak system of social services, care of the elderly is mostly the responsibility of the SONS in the family.What this adds up to in reality is that daughters are expensive and don't contribute to old age security.Sons OTOH actually BRING money and are able and expected to care for their parents at old age.So, hardly surprising, many indian families very much prefer to have sons rather than daughters. The use of pre-natal gender determination and selective abortions is considerable.