Easier to carry in a wallet and use in small denominations. Can be melted back down if you want the gold out of it. I've read about a few small regions in the US where they have gained traction. They've focused on promotion in only a few states and areas from what I understand last I heard about this.
They had more info than I can provide on their site last I checked when I was first told about it and got curious but I haven't kept up with the project. Just sounded interesting to me.
I like more options in the marketplace to compete against and provide alternatives to fiat.