Using high beams while approaching another vehicle or in populated areas is inappropriate because high beams can blind other drivers and create dangerous driving conditions. High beams are designed to illuminate the road farther ahead, which is beneficial in dark, rural areas with little to no traffic. However, when you're in close proximity to another vehicle, whether it's oncoming traffic or a vehicle you are following, the intense light can reduce their visibility, making it difficult for them to operate their vehicle safely.
In populated areas, where other vehicles, pedestrians, and streetlights are more prevalent, it is especially important to lower your beams to avoid causing discomfort or safety issues for others. In contrast, while traveling on highways or in clear weather, maintaining high beams may sometimes be appropriate when no other vehicles are present, as they can enhance visibility. Driving at night alone is also a scenario in which high beams could be used responsibly, provided there are no other vehicles around.