It is a test of our love, loyalty, and trust. In tithes and offerings. God says those who are knowingly unfaithful in tithes and offerings are robbers. It is also hard to believe that people would stoop so low as to steal money that God has designated for spreading the gospel to the lost. Those who are not faithful in tithes and offerings are cursed, and unless they change, they will be shut out of God's kingdom as thieves.
Covetousness is lethal because our hearts follow our investments.
If my focus is on accumulating more and more money, my heart becomes covetous, grasping, and proud. But if my focus is on advancing God's work, my heart becomes caring, loving, liberal, and humble. Our hearts inevitably follow our treasure. Jesus probably feels much as a parent would whose child steals money from his wallet. Losing the money is not the big thing.