Why would any rational person leave a camper on extended jacks anyway?
Because it's a pain to lower it down 20" with manual jacks and even more of a pain to raise it back up to truck bed height. Any time mine is off the truck, it is at truck bed height because of this reason. However, as soon as the truck is out from under it, I have a pair of saw horses placed under it that will easily carry the entire weight of the camper.
But yeah, to leave it at full height without something steadying the camper isn't very smart.