One of he reasons they included the minigames is that the game was mostly aimed towards a younger audience. A younger audience who has to play minigames to live and is horrible at the actual game so they have to compensate for it by rubbing a screen so hard they almost mess their pants in the process. (I know from experience). So yah that pretty much explains it.That also explains why on the PS3 and 360 versions the minigames rarely ever make a difference.
Erm, all of the versions are aimed at kids, it's bakugan for crying out loud...