People have been marrying for many different reasons. Some people marry to comply with customary or religious beliefs or due to demands caused by prevailing circumstances like war, famine or some other calamity or for reasons of financial security or a host of other reasons.
In some societies, it is a taboo not to be married and people marry just not to be ridiculed by the members of the society.
There are also people who believe that marriages are no longer necessary. They believe consenting adults can live together as partners, without the burdens of a legally married status.
Whatever your reason for marriage, it is likely to be influenced by one or more outside factors and not your own independent decision.
Tell us whether marriage is necessary and if yes, what you think is the purpose of marriage. If you think there are many purposes then you may want to list them in the order of importance.