But as to why the theatre isn't full for every showing, I can think of several reasons. First, not all guests are American, and may have no interest in a pro American stage show. Second, it is almost 30 minutes long ( not counting the wait for each show). Guests who are pressed for time on a shorter visit may not want to take that much time for a single attraction. Guests with small children, likewise may not feel that they can sit still for that long for a relatively sedate theatre production. Third, it may not be high on the priority list for repeat visitors who have already seen it multiple times.
Its a nice respite and chance to relax in airconditioned comfort on a hot afternoon. I confess to falling asleep more than once in there.