
The devs pretty much straight up said the biggest hurdle to overcome when producing hybrids is social prejudice, because Eorzea is hilariously racist. The Elezen and Hyur have a lot of underlying social tensions because of the still relatively recent war between them, and the two Miqo'te clans, while not usually openly hostile to each other, are so dichotomous that they generally want nothing to do with one another.