Here's why:
* Mary's role in Christianity: In Catholic theology, Mary holds a special place as the mother of Jesus, who is believed to be the Son of God.
* Mary's importance: She's often seen as a model of faith, obedience, and purity, and her intercession with God is often sought by the faithful.
* The title's significance: "Regina Mundi" emphasizes Mary's supremacy and her role as a powerful intercessor for humanity.
This title is used in many Catholic prayers, hymns, and devotions. There are also churches and shrines dedicated to Mary under this title, such as the Basilica of Our Lady, Queen of the World in Rome.