I misspoke. I meant "why do publishers lie" since announced release dates are not the realm of developers. There have been cases where I got the sense from devs that a game will not release at a certain time but the publisher keeps on claiming that it will. The perfect example of this, that I couldn't think of earlier, is The Division. Ubisoft promised 2014 or something ridiculous and an anonymous dev came out to GameSpot saying that it would release no sooner than 2016. I don't think Sony has ever done this to ND but I think they have to Horizon.
http://www.neogaf.com/forum/showthread.php?t=1090680
Last August, a Guerilla Games game designer said that Horizon: Zero Dawn was releasing in early 2017 in a German interview. A GG dev later posted in the thread saying that they were targeting a 2016 release. From this, I feel like there are two release dates. The true release date that the devs know (early 2017) and the PR one that Sony feeds to us (and I guess investors).
I don't fault the developers for any of this. They do what they need to do and as the great Miyamoto once said, a delayed game is eventually good, but a rushed game is forever bad.