I wouldn't believe for a second that 25% is game wide. If you have that dev post please link. There is a great post above that shows the random but it still comes back to the definition i posted. The Devs made the choice to make it a low chance drop in the bags as a bonus. The real items from the bag are the currency. However, players dont see it that way. They see the item as the main focus of the bag and the currency as means to an end. If we just had the currency there would be no complaints (other than it maybe takes to long).