What benefits does the driver of a motor vehicle have by using a cruise control system?

You answered correctly. Cruise control helps the driver by keeping the speed constant on level roads and making driving easier, especially on long journeys, as the driver does not have to keep the foot on the accelerator. However, cruise control does not automatically adjust speed to the current traffic. That is a feature of adaptive cruise control, which is a different system. Regular cruise control only maintains a set speed and helps reduce driver fatigue, but the driver must still monitor traffic and adjust speed manually when needed.