A Class C can be really useful when you have smaller kids. We've used ours to hang out in at the soccer fields between games, brought it to the beach just to have warm showers after playing in the sand, and used it for one kid to stay in and do homework while the others are at an activity.
We've used it on day trips just to have our own fridge, kitchen, and bathroom anytime we want it.
We show up really early in the morning for big events (like airshows or even trips to the zoo). We park close to the gate and use it all day to nap or rest as needed.
It's also useful for visiting family during the holidays. It keeps them from having to find a place of everyone to sleep and gives you a way to get some personal space when you need it.