I think there is an argument for both cases. In the Graveyard there are many, many places to fall into, even near the ride where the moving tombstones come out of the floor. Also the pop-up figures could put a hurt on you if you arent paying attention and get too close to one.
As for WDI, sometimes I don't really know what they are thinking half the time but I believe that part of the reason also.
Growing older is mandatory,
growing up is optional.