Humility. It breeds a humble attitude when we feel we are not worthy to go to God directly, since He is all holiness and we are insignificant sinners.
This is new. Does God really teach us that there are matters too trivial to bother Him with? Are there some parts of our lives that God doesn't care about? Consider:
2 Chron. 7:14 : ... if my people, who are called by my name, will humble themselves and pray and seek my face and turn from their wicked ways, then will I hear from heaven and will forgive their sin and will heal their land.
Heb. 4:16 : Let us then approach the throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need.
Why are there tons of verses that encourage us to pray to God and zero verses that tell us to pray to dead people? Notice there is no distinction about importance of prayer. Our God is a PERSONAL God, He is never too busy for us.
I never said God was too busy for us. Some people have a close affinity to a saint because they shared a similar trial on earth that we are going through. Jesus Christ never was blind, or was old, or was a woman. He didn't have a debilitating disease, nor was He a husband or a father. Many saints were. By looking at the lives of such saints who shared our own situation, we can discover that we, like the saint, can endure and persevere, just as they did. The saints are examples of what it is like to follow Christ, no matter the situation.
God has given us all creation to enable us to come to Him. The Saints and Mary are His greatest material means for us to discover Him and to follow Him. This does not mean we don't pray to God or follow Christ! But we can certainly become more holy by looking at how a saint followed Christ. Ignoring the saints is like ignoring a life preserver while adrift in the ocean because you prefer to wait for a boat.
Regards
Well, there is a commandment not to use the name of God in vain. Remember Huck Finn praying for a fishing rod? It would seem reasonable for Huck to ask St. Andrew the Apostle, patron of fishermen, to see if his desire to go fishing was worth a miracle.