I don't get it, I try an avoid questions about marriage? My GF brings that up I'm changing the subject or off to the kitchen...

But Why not support it?
then they can also experience the felling of knowing what it's like to stand up in front of your family and friends, spend a **** load, declare your intent to spend your life with this person only to find out they are a 2 bit whore out to **** you over. Then they can enjoy the magnificent glow of divorce and come out of it with only half there stuff

...
I can see why they want in

The above may be a poor attempt at humour... But really who cares if it's allowed, how is it going to affect you, will it devalue your marriage???