Why do we pray for the intercession of Mary and the saints?
Why don’t we just pray directly to God?

The Catholic Church teaches that: “Being more closely united to Christ, those who dwell in heaven fix the whole Church more firmly in holiness… They do not cease to intercede with the Father for us, as they proffer the merits which they acquired on earth through the one mediator between God and men, Christ Jesus… So by their fraternal concern is our weakness greatly helped” (Catechism of the Catholic Church, no. 956).

Those already in heaven are much closer to God than we could ever hope to get on this side of death. Therefore, just as we ask friends and family to pray for us here on earth, we also ask those in heaven to “hand deliver” our prayers to God. It is our hope that in this communion of the Church in heaven and the Church on earth,  “the merciful love of God and his saints is always attentive to our prayers” (Catechism of the Catholic Church, no. 962).

St Josemaria Escriva wrote: “Live a special Communion of Saints: and, in the moments of interior struggle just as in the hours of professional work, each of you will feel the joy and the strength of not being alone” (The Way, no. 545).