An article by Johney Maron (source link here):
If you really think about it, prayer can seem a little odd. What do you do in prayer? You bow, or kneel, or raise your hands, or just sit there and talk, or even think - and you have the knowledge that God hears you and answers your prayer. Prayer is an amazing reality - a reality that can radically transform your life. Why is prayer so important?
Prayer is important because God invented it.
Prayer is not the random invention of a religious fanatic. It is not a fantasy, a crutch for the weak, or a pipe dream. Prayer is a rock-solid reality that God gave to us so we could talk to Him. Every book of the Bible, from Genesis to Revelation, records prayer. In an amazing act of grace, kindness, and love that God gave us this means for us to speak directly to Him. The fact that God invented prayer and asks us to pray is our confidence that prayer is important.
Prayer is important because the Bible commands it.
God's word is replete with commands to pray. Prayer forms a foundational element of the believer's life. Without prayer, the result will be confusion, anger, lack of peacefulness, and even sin. If anyone questions the importance of prayer, think about the importance that Jesus placed upon prayer. Repeatedly in the gospels, we read of Jesus going to a solitary place to pray, spending all night in prayer, and encouraging his disciples to pray. The final act that Jesus did before his trial and crucifixion was hold an all-night prayer vigil to His father. Jesus thought prayer was important, and the Bible is full of repeated commands for believers to pray, too (1 Corinthians 1:11; Ephesians 6:18; Philippians 4:6; Colossians 4:2).
Prayer is important because you need it.
Let's be honest, though. God doesn't need your prayers as much as you need to pray. Prayer has the power to change you, regardless of what you ask for. Prayer cultivates dependency upon God. When you pray, you are asking God for His help. That really takes the focus off yourself, and places it entirely upon God. Prayer gives us a means to worship God, praise God, and thank God. Beyond that, prayer is your only means of talking with God. We have the Bible, which is God's word to us. Mankind has prayer, which is our words to God. Beyond those reasons, think about one of the main purposes for prayer - asking God to meet our daily needs. Prayer is the believer's lifeline.
Prayer is important because humanity requires it.
Prayer is not just a give-me time. We must pray for others, too. How easy it is to let a casual "I'll be praying for you", turn into nothing more than a sanctified way of saying, "it's ok." Others need our prayers. The homeless need our prayers for shelter. The starving need our prayers for food. The sick need our prayers for healing. The struggling need our prayers for peacefulness. Prayer can change the world. That's pretty important.