It harkens back to the buggy and carriage days when the team driver rode up top on a buckboard seat; he had 360-degree visibility and an elevated perspective. The hoi-polloi rode inside the carriage in comfort, safety and protection from the elements. As carriages morphed into "town cars" such as the one depicted, the owner, Lord of the estate, saw no reason to change the tradition that set him apart from the mere mortal, servant up front in the elements.
Very much a caste kinda thing. People in their places, you know.
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