It's better to talk about BioWare "romances." Even though KOTOR II is not a BioWare game, I'd head there for a slightly better take on things than "talk to me after each mission on a hub planet and select the 'don't be an asshole' prompts and then you'll see me in my underwear in a cutscene." NWN2 also isn't a BioWare game
SS2 is a game that is essentially about being On your own. The actual places as well as seems associated with SS2 are all made to instill in the player a fear sense of isolation as well as frustration. Remember that through actively playing co-op, you directly weaken that authorial intention. The only real cause SS2 even has a multi-player setting happens because the writer required it.
You are able to only play a game for the first time once. By actively playing SS2 in multiplayer mode for the very first time, a person shed something forever -- the expertise of finding all its issues, twists, becomes, and horrors without any someone to depend on but your self. Conversely, you can always go back and perform SS2 in multiplayer mode without dropping something.