It is always been harder to fight on two fronts than one. So when your opponent is defending one front/weakness adequately the right strategy is to open the other front. This is because it is quite hard for the defender to transfer the pieces to the other side of the board.
Here is one of my games, played against a much high rated player. I managed to launch minority attack and of course Black tried to attack the White king on the kingside. However, there came a moment when he realized it would not work and Black was forced into a passive position and defend the c6 weakness, which is quite typical of the QGD Exchange variation. I tried hard to exploit this weakness and gain some material, then finally found the right plan to open the queen side. Apart from few tactical errors this was one of my best games.