Prior to WDW starting with the Rapid Fill system and saying the mugs can be used at any resort, my guess is they did that because guests who did split stays under the old mug program would still use the mug purchased at their 1st resort. Unless those people were on the Dining Plan with the mugs being included as part of their package, why would anyone spend $15.49 (cost of the mugs prior to the Rapid Fill system) for the same mug design twice during one trip? Maybe some people would say they would be honest when doing that, however I don't agree.