Free Will On Earth

"I've visited thirty-one inhabited planets in the universe, and I have studied reports of one hundred more. Only on Earth is there any talk of free will." (p. 86) In this part of the book, Billy is speaking to the Tralfamadorians, and one is explaining that humans are the only species he has found that has free will or independence. What does the Tralfamadorian mean by this? And how does this relate to Billy Pilgrim and the story of the Dresden fire? Earlier, Kurt Vonnegut talks about not looking back, but he does anyway, could this have anything to do with the fact?