Given his dad’s untraditional upbringing, the kid doesn’t understand why he would want to die in the wilderness. It’s too complicated for his father to explain right now. He has a sense of obligation—it’s not yet clear to whom, but he’s exhausted from the weight of it. He's also clearly trying to make a connection with Frank, though the effort is fumbling. At this point, he and the kid are still strangers to each other.