I think Aaron is drawn to the wild places because that's where he last had peace. Before Ellie's death and the destruction of life as he's always known it, Aaron was safest and happiest in the wild with his friends. The river, the wide open plains, and the woods offered Aaron peace, certainty, and reliability that he didn't seem to get at home. With the death of his mother, we are given the impression that Falk's home life with his father wasn't exactly a desirable place.
I think that even though we call it the "wild" places, I think Faulk felt most in control of his life there.