#1 Quite simply, he is not at Barcelona's level

It is already an established fact that Barcelona is one of the biggest clubs in the world, having won all trophies winnable in football, so it goes without saying that only players of a certain level are expected to don the colors of Barcelona.
World Class experienced players in all departments who know what it means to win trophies, while under pressure to play intricate football is the barest minimum expected of a Barca player. Although there are exceptions such as the signing of young talented players who are expected to gain experience with the passing of time or promoting La Masia players who are steeped in the culture of the club.
However, Kevin Prince Boateng is none of those. At 31, he is already a 'veteran' in his own right and it is hard to see him gaining any more experience than he already has, while he is as far from being steeped in Barcelona's colors as a River Plate fan is to cheering Boca Juniors.
Till date, Boateng has won just three major honors in his career (one league and two Cup trophies), while his last Champions League participation came over seven years ago, which shows that he is way off the levels required of a Barcelona player.