Because Saul was God’s anointed king over Israel. Loyal servants of Jehovah respect those whom he appoints.
كَمَا أَنَّهُ لَمْ يَسْتَغِلَّ إِطْلَاقًا نُفُوذَهُ كَقَائِدٍ عَسْكَرِيٍّ لِيَسْتَوْلِيَ عَلَى عَرْشِ إِسْرَائِيلَ .‏