h.mama: Heck, why not just say the Our Father directly to the Father? Did Jesus ever tell us to pray in any other way?
There are any number of things one may do. One does not have to do all of them. I certainly don't pray to all the saints, just as I don't ask for prayers from all humans.
Praying to the saints is a form of intercessory prayer. No you don't "have" to do it, just as you don't "have" to ask prayers from other people here on earth. You may do so though. I don't pretend to understand the need for intercessory prayer at all - though it is clearly shown in the Bible - after all, God knows what we need, and certainly our asking Him once for something is enough for Him to get the message without many people asking it.
So why pray to the saints and angels? Here's what I think. Judge it for what you will.
1) They are confirmed friends of Jesus and the Father, since they are in heaven, and they are conscious of what we do (Luke 15.7, 10). Is Christ more likely to listen to me, an unworthy sinner, or His brothers and sisters in grace in heaven? After all, our prayers are brought before God by the blessed according to Revelation 5.8 and 8.3-4 (compare also to Psalm 141.2). Also, humility dictates that an approach be made by steps. You don't just call up the Presidet of the US with a petition. You first work your way up through the channels of his helpers and assistants. Sometimes, it seems right to take the same approach with Christ and the Father, to have someone more powerful and worthy take your insignificant request up to God.
2) For Mary, even more importantly, she is Jesus' Mother. Out of fillial piety (4th Commandment), I think He is bound to hear her requests and give them much more of an audiance than the requests of his friends the saints. Moreover, if Jesus is indeed our Brother, by Baptism and Faith, than Mary is also our mother as well as his. Why not ask for good things from your mother?
3) Many of the Angels and Saints have great power against the Devil given them by God - the Archangel Michael, for example; so we turn to them to help us defeat the temptations of our Enemy. The Church has assigned Saints to particular roles based on their actions in life. So for example St. Luke the Evangelist is the patron of physicians, since he was also a physician. I chalk up this ability to assign saints to certain tasks to the power of the keys "Whatsoever you shall bind on earth shall be bound in heaven." (Matthew 16.19, 18.18)
4) Our Guardian Angel has been given to us by God to guide us each day (Matthew 18.10), and is not only in constant contact with God, but accompanies us each moment; it only makes sense to ask their help in things great and small, difficult and light. many times, they can open doors for us that would otherwise be shut, since they can contact the Guardian Angels of other people and have those angels put good thoughts into the minds of those we are interacting with.
I hope my explanation is helpful to you in understanding our beliefs.
Have a blessed day...I'll talk with you a bit later. <><
Where two or more are gathered in His name, there He is also. Intercessory prayer helps to unite and strengthen the mystical Body of Christ. Such prayer strengthens our "horizontal" relationship with Christ.