Why car run mostly keeping head lights on?

It is not true that cars must be operated while keeping the headlights on constantly. While in some jurisdictions, daytime running lights (DRLs) are required or recommended, these are low-intensity lamps designed to increase a vehicle's visibility during daylight conditions.

Headlights have several primary functions and are generally used in specific situations:

1. Enhanced Visibility at Night: Headlights help illuminate the road and objects ahead during limited visibility at night.

2. Adverse Weather Conditions: During rain, snow, fog, or dust storms, headlights can improve visibility for both the driver and other road users.

3. Dim or Darkened Lighting Environments: Headlights should be turned on if you're driving through tunnels, dimly lit city streets, or low-visibility construction zones.

4. Daytime Visibility in Some Regions: Certain countries or states mandate the use of low-intensity DRLs or full headlights during the daytime. Check the local regulations in your area for specific guidelines.

While it's important to be mindful of headlight usage for safety and legal compliance, there is no general requirement to constantly run your car's headlights unless in low-visibility conditions or as regulated by your local laws.