Because all the things in the world, the strong desires of the flesh, and the strong desires of the eyes, and the pride of biological life are not out from the Father, but are out from the world (1 John 2:16).
Satan designed the world system, which governs the course of the unsaved, to pacify the sin nature of humans (1 John 5:19; Ephesians 2:2). The first world system was developed in response to Cain killing Abel. It was Satan’s desire for Cain to follow him and persuade all others to do the same, not slay his brother as a sacrifice (1 John 3:12). Through Cain, Satan developed commerce (Genesis 4:20), industry (Genesis 4:22), culture (Genesis 4:21), and a judicial system (Genesis 4:23–24). God destroyed this world system with the global flood (2 Peter 3:5–6), forcing Satan to redesign his method for controlling the sin nature of humans, which now includes false religions (Genesis 11:4). This malignantly evil course is now what governs all the unsaved (Ephesians 2:2).
Since the love of the Father is not in the world, we of the Church are not to direct love towards the world nor the things of the world. Using the methods of the world to draw people into church puts that assembly at odds with God, for a friend of the world set himself as an enemy of God (James 4:4).
*The word “murder” in 1 John 3:12 is a specific word used for the slaying of a sacrifice. Cf. Revelation 5:6.