Well the benefit that SE gets from making the glamour and mount cash only instead of gil that RMT guys won't get any money from eternal bonding. They couldn't make it free for everything because the servers would probably be overloading with the amount of people that want to get married for free glamour and a mount. I'd prefer if they stuck to gil method to combat this but, I can understand that they wanted to line their own pockets instead of the RMT business.