Why did McCandless highlight a Wallace Stegner passage from The American West as Living Space?

It seems that this quote comes about as close as it gets to Chris' intent when he contemplates, decides, and leaves for his self-imposed isolation in Alaska. Chris wanted to be free to do what he wished, free from the wishes and expectations of others, free from obligations, and free to follow his own path. I believe that Chris highlighted this section for himself, and possibly as an explanation for his actions.