Should we have Cultural Groups in Crusader Kings 2

I have bought this game and I it is the favorite Paradox Game hands down. It has so much scope to apply strategies. But I have come to a still in this game. The Catalans and the Occitan are in the different group. But the game states that it should have cultural groups. But it does not make any sense that they are not in the same group. They should be always together especially in the 11th century. So is there a need to have cultural groups in this game. Please explain me. Any help will be appreciated. Thanks in advance.

I will suggest that if there will be cultural groups it will make the game rather interesting. When I was playing I have found that France has conquered major portion of land in the Iberian peninsula. They therefore get busy to fix their big and powerful realm together. By keeping their foreign vassals happy they can easily conquer anything far from their own land.

There are no such decision powers given to the ruler to change the culture or can make or break any culture group of the province. But there are many events involved in it which can change it. It can make a huge difference that the groups containing people are in the same culture or not.