Philanthropists seek to benefit humanity. When we give gifts, we mostly support mainstream projects that don't differentiate by gender, such as "youth", "the homeless", "medical research", or the "arts". We assume that these mainstream projects benefit the sexes equally but sometimes they do not. Often women and girls are overlooked because they lack the power, visibility or opportunity to voice their needs or opinions. As a result, mainstream projects are less effective than they might otherwise be and philanthropic impact is lessened.
Effective philanthropy understands the needs of women and men are different and that in order to treat them equally, their different circumstances must be addressed.