Why have some countries provided incentives for families to send their girls to school?

That is because in many societies worldwide, families still don't want to send girls to schools because they don't think that it's a place where girls should go. Governments try to fight this with various incentives but often the cultural tradition is stronger than these incentives and this creates a society not based on equality. This is relatively common in underdeveloped countries.

The statistics for the eastern war are grim. more than three-million men died in the fighting, more than nine-million men were wounded, and every major country which participated lost its form of government.