There are at least five reasons why the Gospel has failed to convert the world to faith in Jesus Christ.
1. SIN - Men love darkness rather than light (Jn. 3:19). Sin is pleasurable (Heb. 11:25).
2. RIGHTEOUSNESS - The lost are under the misconception that Christians are supposed to be righteous, and this has caused millions to reject our message because they see us as hypocrites. But just like everyone else, born-again Christians struggle with the allure and deceitfulness of sin (Rom. 7:14-25; Heb. 3:13; 1 Jn. 3:2).
3. JUDGMENT - The vast majority of the world's population, including many who call themselves Christians, believe they will one day face God's judgment, and as a result, they place their faith in a "work your way to heaven" religion. Religion provides them with a way to enjoy the pleasures of sin, and then do good works to keep the "balance" leaning favorably.
4. LACK OF UNITY - Because of the lack of unity within the Christian religion, the world does not believe God sent Jesus, or that He loves them as much as He loves Jesus (Jn. 17:21-23). What they do not realize is that the Church, the Body of Christ, is made up of only those who have accepted the free gift of salvation by believing in the finished work of Jesus Christ (Eph. 2:8-9). Just as not all people claiming to be Jews are Jews (Rom. 9:6), not all claiming to be Christians are born-again believers (Matt. 7:15, 21-22; 25:11).
5. SOUL WINNING - I believe the greatest reason the world has failed to accept Jesus Christ as Lord and Savior, is because genuine Christians attempt to win the lost apart from the leading of the Holy Spirit. We know that winning souls is wise (Prov. 11:30). We know the Church has been commissioned to spread the Gospel throughout the world (Acts. 1:8). We know that the Gospel is the power of God unto salvation (Rom. 1:16). We even know that we are to preach the Gospel to every creature (Mk. 16:15). But what we fail to understand is that there is a time to speak, and a time to be silent (Eccl. 3:7).
Jesus told some to tell others about Him (Matt. 10:1-4), and He also told those same folks to be silent concerning His identity (Matt. 10:5-6; 16:13-20; Lk. 8:27-30; Lk. 9:18-21). We are to share the Gospel when the Holy Spirit directs us to speak (Matt. 10:16-20; Jn. 16:13; 1 Cor. 2:12-13). And, unless we know we are to speak, it is wise to be silent. If it is not the Holy Spirit speaking through you, it is the flesh, and "the flesh profiteth nothing" (Jn. 6:63). Apparently, timing is everything!