What is the primary reason for using a lower gear when going down steep hills?

Using a lower gear when going down steep hills is necessary to maintain control and reduce brake wear. When you shift to a lower gear, the engine assists with braking by controlling the speed of the vehicle. This is often referred to as "engine braking." By utilizing the engine to slow down the vehicle, drivers can avoid over-relying on the brake system, which can lead to overheating and reduced effectiveness of the brakes. This is particularly important on steep descents where the risk of losing control increases. Overall, employing a lower gear provides greater stability and decreases the likelihood of brake failure, ensuring a safer descent.