Giving cheerfully pleases God and by doing so we are helping to build God's Kingdom and store up treasures in heaven. In Hebrews 7:8 it talks about how although man receives the tithes, Jesus is the one that receives them in heaven. What better way can we invest in the kingdom of God then by giving?
God doesn't need our money. What he wants is us. Even so, the bible talks about how there is a very clear link with people's view of money and their heart. Money was such an important topic that over 15% of all Jesus said related to money. Jesus said that "where your treasure is, there your heart will be also."
As a church that focuses on the great commission, giving allows us to continue to evangelize, plant churches and support works overseas, as well as take care of our local church.