Playing the AI (in BB and many other strategy games) is extremely boring to me:
Compared to playing against humans, the AI is predictable, has little variation in personality and play/strategy, and is not aware (nor does it care) of numerous variables that affect game play. Above all, the AI doesn't have any emotional investment in its team.
I understand that people don't want to play against disconnecting players who complain about their dice rolls constantly. But, the "thrill of victory and the agony of defeat" can only be witnessed
together if there are competing emotional investments...and that never happens when playing the AI.
Sorry, not trying to cause a flame-war, it's just a rant on my own personal feelings of single player.

However, due to the low number of players and being an exclusively online game, I do understand the reasons to have single player when you are unable to get a game.