Apart from the issue of lineage, the second factor affecting the population of the Witch Tribe is the extremely harsh living conditions.
Look at the air teeming with poisonous barriers, and then at this damp and gloomy environment.
Moreover, Gu Dueling happens frequently here and it's permissible to harm the Gu Masters' lives during these battles, so to a great extent, this is a place where few people desperately compete against each other.
However, the Gu People don't see any problem with such a life, as everyone has followed the old ancestral rules for thousands of years.
Perhaps suggesting that there is something wrong with their lifestyle would even be considered disloyal, a heretical violator, and so on.
Of course, this is the life of others, Bai Junjun is not really conducting a census, she understood the situation and continued to stroll upwards.