People don't recognize these arrangements as marriage. That's what's important here.
Government might soon. And many here are arguing that the government gets to define marriage. I wonder what they will do when the government says same sex couples are married? Or when it says you can marry your pet?
Setting up government as the arbitor cuts both ways.
As far as government benefits are concerned, government gets to decide. But REAL marriage is not decided by government, just their rules in passing out favors.