Why? Because having the world’s approval would indicate that you are living according to Satan’s standards ​ — not God’s.
فَنَيْلُ رِضَى ٱلْعَالَمِ يَدُلُّ عَلَى أَنَّكَ تَحْيَا بِمُوجِبِ مَقَايِيسِ ٱلشَّيْطَانِ لَا مَقَايِيسِ ٱللهِ .‏