That's probably because they still have a bit of work in front of them to reach completion and they don't see it as helpful to provide a "hipshot" or best guess response that'll be used for purposes of slander when the date needs to be adjusted out a bit from that original approximation. Those looking for slanderous ammo just love taking an approximate ETA and turning it into a deadline so they can scream liars, phonies and fraudsters as loud as they can to beat the stock down one more time. I suspect when they get close enough to having a finished product so there's no doubt on their part when it'll be done, they'll provide a date.