Only Gun Milan is Not Enough For Marriage(Keval Gun Milaan Vivaah Tay Karne ke Liye Paryaapt Nahi)

I have seen many people now days fixing marriage based on just the score of Gun Milan or Kundli Milan. This is a dangerous trend because the accuracy of Astrology is questioned in case the marriage fails. 

I have been asked by many people, whose marriage is in trouble, that their horoscope matched perfectly and the score was above 18 but why are they still facing issues in the marriage. My