Because the world has its own religion, has its beliefs and has its own arguments through which they defend their "faith". They claim to be Christians, and yet they do not leave their sinful practices like idolatry, deceit, lying, hatred even among the same families, defame and destroy each other without reflecting if that is pleasing before God. That is not being a Christian, to be a Christian, to be a follower of Christ, is to live a true change of life, because the Word of God says that if anyone is in Christ, a new creature is, the believer in Christ is going to to leave behind that sinful life that characterized him before, to give way to a new life filled with the love of Christ and that will identify him from others. Because to serve the living and true God means to work in his work, to fully engage in the ministry for which God has called him, according to Ephesians 4:11 it says: "And he himself constituted some, apostles; to others, prophets; to others, evangelists; to others, pastors and teachers. Thanks for sharing