Modern day marriages collapse for various reasons.
-Society seems to have forgotten the meaning of the lines "till death do us part". A lot of people are in a rush to divorce at the slightest disagreement.
-Some people go into marriage with the wrong people or for the wrong reasons. A marriage built on a faulty foundation will likely collapse in the future.
-Some couples tend to neglect their primary duties in a marriage, thereby leading to dissatisfaction of a partner. Sometimes the deprived partner can't take it any more and a collapse becomes inevitable.