Marriage is a kind of norm from where the couple would socially get accepted as husband and wife... till that they are just in relationship or live in relationship. Now, the Q is why the marriage is required... being a husband or wife of someone is a special thing.. its a start of new journey. When it comes to just being in relationship the couples are free to take their own paths, they aren't each other's responsibility... whereas after marriage both are each other's responsibility... Hence, people marry only when they get a certain level of maturity. The maturity when they feel that.,this one person is enough for me to spend the life with. The couples feel complete when they get married with their loved ones.