It is just because they don't have such knowledge that light should be turned on at night.

In most Chinese cities, the electric scooters are categorized as bicycles by authorities and only allowed to run <=15km/h. No license, no training required for the rider.

The tuk-tuk-like vehicles are in fact illegal in most part of China, the drivers usually do not have any driving license. They just don't know it is safer when light on.