My guess is that there are several possible factors for this reason. Here’s some I thought up off the top off my head:
- It would be difficult to synchronize the movement of the two motors sitting on either side of the river. A single motor whose output is local to the ferry’s impulse is easier to control.
- The ferry can likely move somewhat independently of the cable, and the inverse of its current design makes this more difficult.
- When comparing the two approaches, the one with fewer moving parts in the system is typically the one that is easier/cheaper to build and maintain.
- It might be more difficult to properly maintain the steel cables if they are stressed in this way vs. the current approach.
- There might have been infrastructure already in place that made this approach easier to implement, and parts for a slightly modified boat are going to be easier to find than parts for a proprietary “raft pulled by a steel cable” system.
- It would be difficult to synchronize the movement of the two motors sitting on either side of the river. A single motor whose output is local to the ferry’s impulse is easier to control.
- The ferry can likely move somewhat independently of the cable, and the inverse of its current design makes this more difficult.
- When comparing the two approaches, the one with fewer moving parts in the system is typically the one that is easier/cheaper to build and maintain.
- It might be more difficult to properly maintain the steel cables if they are stressed in this way vs. the current approach.
- There might have been infrastructure already in place that made this approach easier to implement, and parts for a slightly modified boat are going to be easier to find than parts for a proprietary “raft pulled by a steel cable” system.