Social conditions in India mean that, for many people, male infants are valued more than female. Boys stay at home, bring in dowries, work for the family, and take care of parents in their old age. Girls leave home, cost dowries, work for the husband’s family, and take care of the husband’s parents. And families always try to have the children that benefit them.
Working within those rules, families reduce the number of female children by selective abortion, covert infanticide, and starvation or other deadly neglect.
Of course, this leads to problems at marriageable age. Instead of scrapping the dowry and reworking social expectations, parents of boys will be buying kidnapped girls.