A physical barrier always makes management of human traffic easier. Amusement parks, for example are fenced off to manage entry. And though the fence can be climbed or cut or tunneled under, it discourages most people from entering the park without paying. Likewise, a border wall, or a fence, or any physical barrier discourages illegal entry and reduces the resources required to manage the border.
The current system of allowing most of the border to be open terrain is highly inefficient and objectively ineffective.
The resistance of our elected officials to the construction of a wall is a troubling indicator of their lack of seriousness about controlling illegal entry.