i don't know if it was explained firmly or not as i just skimmed this post. but the reason is to make sure that all retailers have this game at the same time. this is a huge release and they don't want any one crying foul. i remember when i worked at gamestop and we had quite a few games with a firm street date, just to make sure every one is equal. but there were a lot of other games that we got quite early. most of the games arrive at the store the day of, this way all the stores can have it as soon as the open.