The toll collector’s shelter

An original account written in a nineteenth-century voice; a period simulation, not an archival document.

The new shelter stood a little way from the toll gate. It kept the collector dry, but he could not see the road from its doorway because a wall stood between them. To judge when a cart arrived he had to step into the rain or listen for its wheels. The builder offered to enlarge the doorway. The collector instead requested a window in the side facing the gate: a wider opening in the wrong direction would not give him the view he needed.

Explain why enlarging the doorway would not solve the collector’s problem.