Personification, as stated in your question, is the assigning of human characteristics (or qualities) to non-human and non-living things. Authors tend to use personification so that readers can relate more easily to the idea or characters (if not human) in a story.
George Orwell uses personification in his novel Animal Farm. The animals of Mr. Jones' farm, Manor Farm, decide to overtake the farm and run the humans off. After taking over the farm, the animals are depicted as facing problems which humans face in their own societies.
In the novel, personification is absolutely necessary. Without the use of personification, some readers may not connect or engage with the characters in the novel given they are animals. Orwell knows that for readers to understand his message, readers need to relate to his characters. Without this relation, the message is lost.