Video games are the same there are regions with far lower prices for new titles like Latin America, Russia and some parts of Asia.
A lot of the keys sold on various sites come from those regions, some companies iirc Ubisoft started implementing region locks.
Region locks on DVDs other than due to issues of distribution rights especially for dubbing and subtitles followed the same logic especially in Russia where region locked DVDs were released much earlier and for much cheaper as piracy was far more common there than in the west.
A lot of the keys sold on various sites come from those regions, some companies iirc Ubisoft started implementing region locks.
Region locks on DVDs other than due to issues of distribution rights especially for dubbing and subtitles followed the same logic especially in Russia where region locked DVDs were released much earlier and for much cheaper as piracy was far more common there than in the west.