Mostly because I failed at balancing them and I could see who would win pretty early on.

I made a huge gaffe in the Daes Dae'mar game especially. The House with the spymaster was not supposed to have Darkfriends in it (because obviously the Darkfriend would guide investigations away from his fellows). That was one of three ways in which Darkfriends could be revealed, so I failed pretty bad there.