1. St. John Paul II's Theology of the Body offers the most comprehensive understanding of our creation as male and female and our call to the life-giving communion of persons known as the family.
2. It was the first major catecheses of the Bishop of Rome, John Paul II, shepherd of the universal Church, and one he slowly unpacked over a five year period at the beginning of his pontificate with incredible precision and passion.
3. The assassination attempt on St. John Paul II took place in the middle of those catecheses. That's got to mean something.
4. The theme for the World Meeting of Families is "Love Is Our Mission: The Family Fully Alive!" The Theology of the Body's central theme, which runs like a ribbon through all of his other work, is the family, as St. John Paul II wrote in his Letter to Families, 19; "The Church cannot therefore be understood as the Mystical Body of Christ... unless we keep in mind the "great mystery" involved in the creation of man as male and female and the vocation of both to conjugal love, to fatherhood and to motherhood."
5. The Theology of the Body reveals how masculinity and femininity are "not only a source of fruitfulness and of procreation, as in the whole natural order," but contain "the power to express love: precisely that love in which the human person becomes gift and - through this gift - fulfills the very meaning of his being and existence." (St. John Paul II, TOB, Jan. 16, 1980) Wow, I'd recommend reading that one again.
6. St. John Paul II once whispered to a friend at a meal that if he were remembered at all, he wanted to be remembered as the Pope of the Family, and the World Meeting of Families was in fact his idea starting back in 1992.
7. See reasons 1-6 above.