DProject: Then again, this doesn't explain why they still continue to sell games like Postal, Carmageddon, etc
NoxTM: I think
Hatred is working on a more 'realistic' approach (well, as realistic as you can get with this kind of genre) whereas the other two were more bad taste but comic book in their approach.
Having said that, and even though I've already written this doesn't fully look like my kind of game*, I think this is a poor decision from GOG that stems purely from fear.
*Seems kinda dull and one-note to me.
The first Postal wasn't like the second one. The classic game was a lot like what Hatred seems will be, different graphics, sure, but not less violent or gory, and there was no comedy or real reason behind the violence. Not a bad thing imo, just pointing out that the first game (currently being sold in GOG) had pointless, gore-y and hard violence. If anything, Hatred seems to have more story behind it than Postal 1 did.
EDIT: The whole talk about quality of the unreleased game made me remember something: wasn't Omerta the first game that featured purchasable DLCs in GOG.com? A not well received game at a high price?