To understand why nine minors cannot travel in a nine-seater car, including the driver's seat, it is important to consider the rules regarding the transportation of people in vehicles.

- **Number of authorized seats:** A vehicle can only transport the number of people for which it has available seats. In a nine-seater car, this includes the driver and eight passengers. No more people can be added, even if they are minors, because it would exceed the number of authorized seats.

- **Safety and comfort:** Each passenger must occupy a seat throughout the journey. This is crucial for safety, as each seat is designed to protect a person in the event of an accident. Additionally, children who are less than 135 centimeters tall must use child restraint systems appropriate to their size and weight, which requires additional space in the vehicle.

- **Passenger distribution:** The driver must ensure that all passengers are properly seated and that the load is well distributed to maintain visibility and control of the vehicle.

For these reasons, it is not possible to transport more people than the vehicle is designed to carry, regardless of the age of the passengers.