They do it, because when PS4 and Xone owners would have seen that E3 demo graphics and animations being played on High end PC compared to the downgraded PS4 and Xone (our current) version they would get for their (next gen) consoles, they would simply wouldn't buy that game on that platform. That would had as a result less profits for the publisher the devs and the Console makers. Instead they downgrade the s**t out of the game trying to make it run at least 30fps across console platforms (cinematic experience), port it to pc with some slightly better visuals mostly PP shaders like SSAO and DOF, to achieve comparable quality across all platforms and make everyone happy. P.S. For any console fanboy i might hurt, i myself own a PS4 from the 1st day of release but it does not change the fact that they are far from what i would call a NextGen.