Mainly because the publishers of Taiwanese, Chinese, Korean VNs are more conservative in creating such VNs to hope for more western consumers to buy the game. So they choose stories that are more vanilla and tame, compared to the lustful demon known as japan... Which btw I only consume Nippons finest materials ;). And since they are only a few indie game makers in those country (where my country, which is in the east as well, has NO INDIE GAME DEVS at all) the experience and available resources to create even a simple VN are probably limited and not cheap over there. Give them time and surely a group of people or a company will be able to make some JP tier stuff.
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what a endurance you have for this things