We purchase it most of the time for the following two reasons:
1) I want to lug around as little as possible while I'm at the parks and with two children under the age of 5 it is a massive pain to carry around a big DSLR camera along with a diaper bag, change of clothes, snacks, etc, etc. I refuse to risk taking pictures with our phones as the lenses simply aren't fast enough to avoid motion blur.
2) I'm always the one taking the pictures so I'd rarely be in our family pictures. One day when I'm gone, I'm guessing that the kids/grandkids will like seeing pictures of their dad/grandpa hamming it up with them at Disney.
We'll take candids with a little point and shoot and use the Disney photographers for the touristy shots. Also, the ride photos are always fun!