Because they view marriage as a sacred gift from Jehovah. Jesus said regarding married couples: “What God has yoked together let no man put apart. ”
فَٱلْكِتَابُ ٱلْمُقَدَّسُ يَقُولُ صَرَاحَةً فِي ١ كورنثوس ٧ :‏ ٢٨ إِنَّ ٱلْأَزْوَاجَ وَٱلزَّوْجَاتِ سَيَكُونُ لَهُمْ « ضِيقٌ فِي جَسَدِهِمْ » .‏