Now a days boys and girls are more bended towards sex in there life. Many of them makes this relations in the name of affairs or boy/girl friend. Some time they think having a boy/gal friend is the symbol of status. This kind of relation are not true love and are based on just some other factors. So if they were not able to get married, you can imagine what a bad marriage they would be in. If they some how get married also then things changes a lot becuase of reality of life.
I feel this treand is also becuase of the Mordern life style young person are following.