Ok, but what happens on your 3rd and 4th picks from tradition (the 4th is very important, you really need to rush Landed Elite)? The barb culture will not compensate for those and you will actually get them later. Because your 3rd and 4th tradition picks are now actually your 4th and 5th SPs picked they will cost a lot more, and you are still getting an average of 10-12 culture for barb killed. Even with raging barbs it is barely cutting it, but as the game progresses the losses are bigger and bigger, and later you are "stuck" with a policy that doesn't do anything since barbs will play almost no role in the game. The number of SPs you can unlock is limited, and each time you pick a SP, you give up on something else, so there is an opportunity cost associated with every pick.