I probably don't understand the tax system well enough to speak clearly on that, but I agree with BP that there's no reason for the social/religious aspects of marriage and the legal aspect of marriage to intersect.
What is marriage, socially speaking? It's two people announcing that they now wish to be considered a singular family unit. The home culture(s) of the two people usually expects the completion of certain rituals to make the process of marrying socially legitimate, and may now assign social roles, assumptions, expectations, privileges, etc. based on the couple's new status -- e.g. in most cultures it's assumed that a married couple intends to create and parent children; in many cultures marriage is required to be considered a fully mature adult; the extended family or broader community may have some obligation to help the new couple establish a household; and so on.
What is marriage, religiously speaking? Depends entirely on the religion and on each person's participation within the religion. Nearly all religions require or expect the completion of certain ritual aspects in order to make the marriage legitimate in the eyes of that religion. Many religions view marriage as a partnership that extends beyond the physical/material and has a special interaction with the religion's beliefs or god(s).
What is marriage, legally speaking (in the U.S.)? You go to a designated government building, pay some money, and get someone authorized by the state and any two other people to sign a piece of paper that says you're married. Both of you are now entitled to a tax break, and your power of attorney claims will be taken more seriously than those made by two people who are not married. For most financial processes involving state or federal governments, your property and assets are now considered a pool, and in many situations (varying by state) creditors will be legally allowed to seize assets from either of you to repay a debt held by one of you. If the marriage is legally dissolved (i.e., if you divorce), both of you are entitled to go through a legal process in order to divide or reassign your property, assets, and access to any children.
Not a lot in common between that third one and those first two, eh? If it were up to me, there would be absolutely no government involvement in two (or more) people choosing to be a family unit, within or without a religion -- but I'm a crazy hippie like that.
Im surprised there arent more single people arguing that they should recieve the same benifits of married people because they dont want to be treated different just because of the marital status.
(Once again, only speaking about the U.S. here.)
I think most single people agree with this, but there are a few reasons it hasn't happened, I think. One is that "unmarried" is kind of a watery legal status, similar to "separated," whereas "married" and "divorced" have fairly solid legal definitions; any assignment or reorganization of rights would require a definition first. Another is that society frankly ranks married people above single people in terms of presumed maturity and value to the group, especially if the single person is above a certain age -- and almost any married person's solution to any disparity is for the single person to just get married. The third is that the legal benefits of marriage are actually relatively few beyond power of attorney, which usually only comes up in a single person's life when someone they're close to is incapacitated, dying, or dead. The tax breaks can be significant but I doubt most people (married or single) understand taxes well enough to care.
Now if you're talking about the de facto benefits married people get outside the legal system (access to health insurance through one spouse's employer, better terms for loans, etc) -- yeah, those are a load of crap, but what company is going to volunteer to make less money off single people?
