Tehcnical problems, in my opinion, are not a legitimate reason. All of the trailers and such stress how much Joel and Ellie are working together to survive, so co-op SHOULD be a no brainer. And yet they made the game in such a way that it's apparently impossible. They tied their own hands.
And I remember the excuse about factions, scarcity, theme, etc. being used for a lot of things. I don't mind it as a reason not to add anytbing excessively silly, like traffic cone hats or donut skins or something. But not adding gametypes like king of the hill or capture the flag or something because they don't think it fits the theme of the game, or that's not how they want the game to be played, is just over the top stupid. Skins SHOULD be the same way. I feel like they could easily add skins from Uncharted or TLOU single player without making them look out of place.
Technical limitations of the PS3 are the biggest factor holding back Co-Op.
PS3 has 512 MB RAM and uses a CPU 7+ years old.
Look how awfully choppy action gets when too much action is on the screen in Factions. Just think if you had hordes of infected plus your co-op buddies on screen. People would be complaining that the AI is lagging with infected sliding across the screen because of technical limitations.
Which part is silly?
adding a bunch of random skins and complaining at the fact that they can't technically implement the mode in the game.
don't forget, ps3 is dated hardware... I'm sure your ps3 roars like a thunderstorm everytime you play this game like many other people every now and then, especially if you have an older model.