We give because God asks us to and obeying shows that we trust Him. We give because everything we have comes from God. Giving is an act of worship. Our God is a generous God, so we want to be known as a generous church that gives regularly, joyfully, and sacrificially.
2 Corinthians 9:7 "Each of you should give what you have decided in your heart to give, not reluctantly or under compulsion, for God loves a cheerful giver."