Because like the PS2 any company like Activision will milk old gen for all they can. The Xbox is ridiculously old. Destiny alone has cleared a billion dollars on old gen assuming old numbers of about 7 million be true. As of late 8 million or so next gen added another 1.2 billion roughly. Not including upper end preorder or any of that. So 10 years and 500 million dollar budget was greatly exceeded in profits. They have zero need to waste money on old gen. I forget to include the Everest money, but that information is more secret. So why should they support old gen when they can move all old gen team to Destiny 2 development? The Xbox One has been out for 970 days. That makes $500/970 "52 cents a day" and currant $300/970 "31 cents a day. As for the PS4 out for an extra 7 days at 977 days. Launched at $400/977 "41 cents a day"and at $300/977 "31 cents a day". This game is so profitable that they simply wanted to get what they could. Old gen was that answer as they would be near a billion dollars of from current profits. There is zero excuse to not have a next gen console by now.