Again, why we do marry?

She's got an Oscar, two kiddies, a billion trillion dollars, and yet, it was just announced that her marriage to Ryan Phillippe has gone KABOOM!
Add Reese Witherspoon to the separated list.
You can have it all and yet have absolutely nothing, I guess.
Tell me again why as little girls we dream of getting married? (See earlier post, I Now Pronounce You Marriage Obsessed.)