Motorsport is a sub-set of sport.
Sportscar racing is a sub-set of motorsport.
Endurance sportscar racing is a sub-set of sportscar racing.
Not only does endurance sportscar racing test the limits of machinery to make the distance, but racing at night is a different experience for the drivers behind the wheel. Visibility is at a premium. Some tracks have surrendered to the temptation to add artificial lighting. Other tracks - particularly the longer natural terrain road courses - run mostly in the dark, with a bubble of light around the pits and front straight.
At speed, being able to pick out a corner apex or see debris in the darkness can make the difference between success and ending the race prematurely. Technology has improved the quantity of light a car can give its driver. Over time, lights have become smaller and produce more and more light. In addition, night racing is a novelty for many teams - particularly amateur teams that race events such as the 25 Hours of Thunderhill.
Endurance racing is a puzzle with the same answer but many possible solutions. One of the interesting aspects of a race like the 25 Hours of Thunderhill is the variety of cars and corresponding lighting arrangements. In some cases, lights are build to be affixed and removed depending on the darkness. In other cases, lights are permanently attached.
The Funduro Racing Roadster, Mazda Miatas, Honda Civics and BMWs were great examples of different headlight approaches. Even the safety car had its own light bar mounted across the hood. See photos in the gallery at the link.