Originally Posted by skavenhorde 
As for why they didn't make implement it. Easy answer, how many games tried to implement MP and had a great singleplayer experience? Not many. I would rather they focus on one and not the other.
Eh … Baldur's Gate?

Another example is Hidden & Dangerous. If done like Blizzard with online community support (store characters, group with online friends etc) you may get some additional piracy protection too. Another game that works like this is Guild Wars. Someone might disagree, but it's basically just a coop-game with online hub locations or Baldur's Gate with some added online options.