Why the government should get rid of marriage!

So with all the talk throughout the country about how gay marriage should be allowed for all, gay rights etc. I thought to myself why do people generally care about whether or not another individual would like to get married? Most arguments I've heard have been typically related to some kind of religious cause. So... if religion is one of the biggest reasons people are against gay marriage, rather then force states to define the word marriage in the eyes of a state, or eyes of the federal government, would it not be easier simply to abolish "marriage" from the governments books. Change marriage as the government knows it to something along the lines of calling it a civil union, or really whatever they would like as long as its not called marriage. Define whatever this replacement for marriage would be essentially with the all the rights married individuals have now, but define as between two consenting adults. Leave marriage to the religious and keep the important side of it separate so that everyone is entitled to the same rights, be it visiting you partner in the hospital, to adopting a child, to getting shared benefits and much more.