We are born naturally self-centered not God centered.
For I have no man likeminded, who will naturally care for your state. For all seek their own, not the things which are Jesus Christ’s. (Philippians 2:20-21 KJV)
Things have not changed dramatically since the early church. It was hard to find God fearing individuals who put the needs of God and others above their own needs in biblical times as it is today. Paul was not able to find like-minded men among his brethren, spiritually mature enough, to place spiritual needs of others above their own. Paul sought out men who were willing to embark upon a long missionary journey giving the gospel message to others. Paul ran into obstacles in biblical times and those same road blocks prevent some good men from witnessing the gospel message to others today.
Paul found that often men would not be willing to set aside the time required in serving God and spreading the gospel message. Some would embark on such a journey to reach others but lose their spiritual steam halfway through the expedition; turning from their calling for God focusing instead upon their own needs choosing to revert attention away from the things of God placing it upon dark things of the god of this world instead.
Paul spoke of this very issue concerning some who departed from their calling in the book of Second Timothy:
For Demas hath forsaken me, having loved this present world, and is departed unto Thessalonica; Crescens to Galatia, Titus unto Dalmatia. Only Luke is with me. Take Mark, and bring him with thee: for he is profitable to me for the ministry. (2 Timothy 4:10-11 KJV)
Not all men who are called to begin a journey for God will heed the call or persevere in the long term forging ahead on the intended spiritual pathway of God’s calling upon their life. However, there are many great servants of God who are busy about His business sowing seeds of the gospel message for God to supernaturally cultivate and water in the lives of willing individuals; producing saving faith and bringing about repentance of the soul.