They picked these races because they are some of the most, put my self in their shoes, type of races. There aren't really a lot of races in FF lore, sure they have Bangaa and Viera, even PuPu's, but not a lot to choose from. Plus the devs are generally shooting back to old FF games. Not only were the races in FFXI a natural choice, but they seemed to be the only choice as far as the amount and to avoid people being freaky reptiles and the dogish Nu Mou.