Most of those people do it out of convenience. They want to play on their console, in the living room with the big screen, and they don't want to fuck around with torrenting ISOs and hacking their machine so it can play copied games. Next to convenience, morality takes a distant second place; they probably pirate music and movies without hesitation. But fans of Crysis 2 have long been awaiting its release, and being able to play it months before its street date, even if it means playing on PC and hitting the torrents, might tip the convenience equation.
That is why this is so dangerous for Crytek.