Bodies in the nether do not rot, so a dead person's flesh is eaten by their family and friends in a ritual to free their soul and guide them to the afterlife. The leftovers such as bones, are then grinded and used to grow crops, mushrooms or fight the spreading of nether wastes. It is believed that if the ritual isn't done right, their souls will get stuck to this world, birthing wither skeletons.
Piglins are encouraged to hunt and kill wither skeletons to free the souls stuck to them. It is also why Piglins are this terrified by their Zombified counterparts, "rot" is a strange worldly concept to them, something that simply should not exist in their holy land.
