As my title suggests why is this the only option? We were promised a co-op multiplayer mode when this was still in beta and we've yet to see even any mention of it. Honestly I pre-ordered this as soon as I could thinking I could play with friends and its been nearly a year and you have done the official "release" if you can call it that. Yet we are still missing 60% or more of the content we were promised.
The game is not missing 60% or more. Please cease with the hyperbole.
As for MP they have had a major problem with it when the AI is added.
It was crashing every few turns.
They have a volunteer team working on it.
No estimate as to when atm it will be fixed.