Is Marriage Obsolete?

I was talking to a friend of mine recently.  He and his girlfriend live together and, he says, will probably never get married.  He says that they're already committed to each other for the long haul.  Marriage is just the expensive way to break up if it doesn't work out.

Is that really all there is to it?

If that's it, then you must be defining marriage to consist of the legal contract of joint material ownership.  Lots of people sign pre-nuptual agreements, though.  Are they still married if they don't agree that they own everything jointly?  What about common-law?  Not married, just living together.

Now we've gone from husband and wife to partners.  Long term commitment.  Best friends.  Same thing, right?  I mean, most places offer benefits to domestic partners.  Two-income households have no tax benefit from a legal marriage.  From the outside, it looks the same.  No rings--I guess, it's not exactly the same.  Close.  Perhaps that's why we're wondering if marriage has become obsolete.

In my estimation, these friends of mine that are living together are already as close to married as most people ever get--with or without the 'red tape.'  My definition of marriage includes an element of faith--a promise between two people and God.  My friends, however, don't believe in God.  That is the fundamental difference, as far as I can tell.  In the absence of that element of faith, I don't really see a difference.  I see no concrete advantage to telling the state of your intentions.

Is it marriage, or the sanctions of the state that have become obsolete?