Myranda, I am fairly certain that, in a storytelling perspective, they do so in order to diminish the importance of your origin to as little as humanly possible.
Where you are from is not important. Who you used to be is not important. You story is blank, your past irrelevant, your future is all that matters. A future which is what we play through. Hence why I believe the alleigance you choose to the grand companies is of more important than your origin nation and all that.