I am virtually positive that Quinn is bringing us to some existentialist conclusions in this book.
The reason that I believe this to be so, is because of the way he has framed the Taker and Leaver culture. He has made participation in Taker or Leaver culture a choice, and therefore, the essence of humanity now is based upon a taker culture that has centered the materials of the world around the preservation of its being.
What interests me is that I think Quinn is saying is that the Leavers are not afraid to not exist, they simply co-exist with the iminent non-being that all beings eventually become. The Takers on the other hand, are perhaps filled with an anxiety because despite having controlled some elements of existence, takers are not yet able to control the end result of their existence, which is non-being.