Even with the “free” drink package you still have to pay 18% of the cost of the package for gratuities. That’s why you have the option of not getting the unlimited drink package even when it’s offered “free”. If you aren’t drinking soda or alcohol, you don’t want to pay the extra for the gratuities. As I recall it’s something like $150/pp. That’s why you don’t see people paying cash gratuities- it was already paid up front.