Using headlights during the day when visibility is reduced helps to:

Using headlights during the day when visibility is reduced helps to make your vehicle more easily seen by other drivers and pedestrians. Visibility can be affected by factors such as rain, fog, or overcast weather, and using headlights in these conditions increases the likelihood that other road users will notice your vehicle. This is particularly important in preventing accidents, as it enhances the overall safety of driving by ensuring that your vehicle stands out, even in daylight.

While improving fuel efficiency, reducing glare from the sun, and maintaining battery life are all valid concerns for drivers, they do not directly relate to the primary purpose of using headlights during the day. The main focus is always on safety and ensuring that your vehicle is visible to others on the road.