I think, in theory, they want to control the number of "browsers" at the resort overall, because folks "just visiting" the resort, whether it be for dinner or the pools, etc. are also apt to overuse the wildlife viewing areas, which may then cause the animals to "shy away" from the lodge. I remember when AKL first opened, there was a $10 refundable deposit to book a dining ressie if you were not a guest at that resort and wanted to dine at Boma or Jiko.