Cheaper and/or faster. And in my example, the sender or recipient might chose to just do it themselves.
The Øresund bridge is competitive with the ferries between Denmark and Norway, despite being a detour when looking at the maps (except if going to northern Norway). Given the right circumstances, the bridge route is faster, however the ferries have an advantage in that it lets a single driver keep moving and take the mandatory rest at the same time. I don't know exactly how the cost of using either compares. It is also possible to send only the trailer with the ferry, eliminating the driver and associated costs altogether.