Crosmando: A better question is why they plan on porting it to consoles in the first place.
The Xbox 360 port of Witcher 2 sold terribly and was completely dwarfed by PC sales, it also got a lot of negative reception from the usual merican consoletards who said W2 was too difficult and the mechanics were too hard to understand.
Witcher 2 suffered so badly because it was designed with the idea that it would be ported to consoles, so we got that horrible inventory and control scheme, and other "consolized" stuff like QTE's.
Gotta agree. The game ported terribly and not many bought it on console so why on EARTH would you make it playable for the Xbone, which is against absolutely EVERYTHING DRM-free. Makes no sense.
I'd say, if the game got rave reviews which come on we all know it will, they would have been better making it only for the PC AND releasing it on GOG weeks before it went to Steam. Exclusive means something in the gaming world. Why do you think so many people by Xbone's and PlayStations? For the exclusive games on them.
Look at The Last of Us, for instance, that game is only ever going to be on one console. Has it stopped hundreds of thousands of people buying it? No, as it looks like it's going to be the game of the year. The Witcher 3 has that potential, but CDPR has given up that 'exclusivity' just to shove it on as many places as possible. Disappointing to say the least.