Perfect for the Nanny!

I was looking at the Los Angeles Zoo website. There are different membership levels that you can pay for to support the zoo. At the family level, you get unlimited free admission for two adults and all of your children for a year. At membership levels above that, you can get admission for three adults. They could have emphasized the extra admittance for a loving grandparent, another family member, a neighbor, or even the non-custodial parent (a benefit for those who are divorced). No, they say that the third admission is "perfect for a nanny!" I just do not understand. I suppose this is marketed perfectly for the L.A. stereotype of what a normal family should look like.