Tom & Pat,
I understand that for YOU the thought of playing the Par-3 course vs. playing a second round at one of the other courses does not make sense. But you guys are not the "average" guest. Many cannot nor do they want to WALK 36 holes in a day. There are many groups, that in tough windy conditions struggle with just 18 holes.
But from my experience, and Joe can back me up here as we have both met/worked for 1000s of resort guests, the 36/36/36 crowd makes up a small percentage (10-15%) of the total visitors.
The "average" guest may not even be aware of the par-3 course's existence before arriving on property. I think many people on this site overestimate the GCA knowledge of most guests. We get asked who designed each course ALL THE TIME!!