We don’t, you do. Catholic simply means universal, as was clearly understood by the early church. We refer to ourselves as Catholic (universal) Christians. I am a disciple of Jesus of Nazareth, the Magisterium of Holy Mother Church merely exists to serve all of the savior’ s disciples. As the title of the pope suggests; Servant of the Servants of God.
Catholic is not a title in the Word. Nor is roman cathoic.