The reason could be as simple as their not able to be backed to, every body may have different set up on their truck some have a longer boom on the hoist, a bigger wench, more cable, lazy driver, down in a sinkhole or gully, lift gates. Years ago i worked in a butcher shop. the truck they had a lift gate and boom with a wench and they had dead cows in it sometimes. I talked the driver a couple of times what they did with everthing, he said they rendered most of the animal down for all types of things that were and are used in a types of everyday things. Just like limestone or marble i can't remember which but it's crushed super fine and put on the outside of chewing gum to keep it from sticking togeather But very little if any part of the animal goes to waste. It could be a 100 different reasons that they need to drag it to get to and in the truck.