4 points
One possible reason for this is the lack of useful draft animals. Even with a cart a person can’t move much more than they can carry, especially across rough terrain. You’ll note that the wheel wasn’t developed in the west until after the domestication of oxen and horses, and since they had both died out in the Americas there wasn’t anything strong enough to pull the carts.
For carrying large amounts of cargo native Americans would use a travois, which could be dragged behind a person or dog or, eventually, a horse.
