Considering when you balance for MP you balance for SP as well but the opposite is not true.

I can't quite see the big stir from people crying "Oh it's never about SP, it's all MP" when your problem (Making out of control pretenders) was fixed within 2 days after the patch release by a 3rd Party while retaining the MP balance of not having cheaters.

It's MP, Modability, Balance, Customer Support, etc, etc that keep people playing the game and more importantly buying the game.

I'd love to see some AI updates, Diplomacy and other SP features in the game, but I don't think you'd have the game you have now (so deep and diverse) if they thought about SP first. They'd be thinking about making 'campaigns' and other things that would, over time, kill the MP aspect.