Talk:Monster Girl Encyclopedia World Guide I: Fallen Maidens/@comment-45424649-20200522140945/@comment-10429980-20200522144227

A lot of them simply aren't able to journey and find a man until much later, or they may have bad luck or particular standards (take Bapho-sama, she's well over a thousand years old and still unmarried). These journeys may also take a long time, since KC has mentioned the MGE world is notably bigger than Earth and that many vast areas are mostly uninhabited wilderness. KC's even remarked on how a fair few monster girl fathers will not allow their daughters to journey into the world to look for men, which is going to result in a fair few scenarios of christmas cake daughters trying to romance their little brother once it becomes possible for incubi to be born.

Basically just because they are old enough for sex in theory doesn't mean they will actually have it in practice. As for being unsettling, I suppose that's the idea (in fact it outright gives Sabbath monsters more power), but for monsters it's mostly just a difference in their biology from humans and unlike in humans doing it early doesn't seem to do them any harm. Some may also physically mature much faster than humans (i.e. it presumably doesn't take long for a newborn slime to gain enough mass to appear as "adult" as a much older slime), especially given how quickly they become independent (though the references to their small size argues against this theory).