"Make every effort to come to me soon; for Demas, having loved this present world has deserted me and gone to Thessalonica." 2 Timothy 4:9-10
The followers of Jesus are in the world but are not of the world. Believers are sent forth into the darkness of this present world to bring the light of truth. Jesus told His disciples that the world would hate them just as it had hated Him. The Christian commission to the world is bring the message of the gospel - to save those who receive it and bear witness against those who reject or neglect it.
James wrote that to be friends with the world is to make yourself an enemy of God. When God saves us through Christ He transfers us into the Kingdom of His Son, so to be friends with this present dark kingdom would be to befriend the enemy. We are Ambassadors of the Kingdom of God and are witnesses against this world which is in rebellion against God.
Many reject salvation because of their love for the world and what the lusts of the flesh has to offer. They may see Christianity as being restrictive, denying them things they want. Though the Bible plainly says that Jesus is the only way to salvation, some convince themselves that submission to Him is not necessary for eternal life. To some practicing Christianity is an unnecessary burden.
The Way of the Master TV program gave the following analogy. Suppose you were flying in an airplane and the stewardess came around offering parachutes promising that it would make your flight more comfortable. You noticed that a few took the parachute but most did not. You decide to take the parachute since you were promised that it would make your flight more comfortable, but soon discovered that wearing it made you uncomfortable in your seat. On top of that you noticed that passengers who were not wearing parachutes were laughing at you. If this happened to you, you would probably complain and take it off.
But what if the stewardess had told you that the plane was losing altitude and was going to eventually crash and that the parachute would save your life? In this case you would not be so concerned whether it made you a little less comfortable. Nor would you be bothered so much by those who were laughing because you were wearing it. Knowing that everyone without a parachute would perish in the crash, you would see these people as being very foolish. It is a matter of perspective. "The one (AntiChrist) whose coming is in accord with the activity of Satan, with all power and signs and false wonders, and with all the deception of wickedness for those who perish, because they did not receive the love of the truth so as to be saved." (2 Thes.2:9-10)