With horses, one person could control both the motive power and the implement, but with a tractor, two were required, because the tractor required a driver and the implement, in many cases, required an operator.
One person could control both the motive power and the implement. This is with horses. Two were required. This was with a tractor. The tractor required a driver. This was in many cases. The tractor required the implement. This was in many cases. Many cases were required an operator.