Which must include the opportunity cost of a parent staying at home to care for their own children. Creating financial incentives for parents to turn their children over to strangers would be a recipe for societal disaster.
While I agree that a mother raising the children is preferable, that some families may need two incomes, or conversely may not have two income earners. If there is a father than the mother should get tax advantages equal to day care costs, if she opts to stay home and raise the children.