Keep in mind, at least some races need to be off limits for lore purposes, otherwise the characters aren't as special. Sometimes that race difference is their entire identity, pretty much. (Like Gridania's padjal dude, whoever he is when he's not... padjaling around...)
The whole thing about the PS3 races is that we felt it was ridiculous to let us choose a race... but limit the gender. Even form a lore standpoint, the justifications were tenuously liked to lore, at best.