I don't understand why they don't want more races

[Fland]

The new races will add more income significantly if they are the highly requested races. From the race poll result back then (https://forum.square-enix.com/ffxiv/...ure-Race-Polls), the 3 highly requested ones are mammalian beast race, a mixed-race, and third clan for existing race. They already made two new races out of one of those three categories. So the remaining highly requested race are the third clan and the mixed-race.
However, I think there was some interview where Yoshi-P mentioned that they won't be doing any mixed-race PC (sorry can't find it atm).