Part of Punk's vow never to return comes down to ego. He think's he's above the industry, he sees himself on a certain plateau where he's a brand to himself. It's a point of principle which several former wrestlers have taken up in the past, notably Bret Hart and The Ultimate Warrior. Those two men had far more personal disputes than Punk's current predicament. Hart was screwed by Vince Mcmahon in humiliating fashion at Survivor Series 97. Warrior meanwhile had years and years of legal issues against McMahon. In both instances, Hart and Warrior eventually went back to WWE years later. Why should Punk be any different? Part of why is because Punk doesn't want to be that stereotype, he wants to be his own man. He knows the common perception is that he'll go back eventually, so he's naturally then fired up to prove those fans wrong. In his mind, he's above returning, he's better than just being another Hart or Warrior to WWE's machine. As Paul Heyman said in the Helwani interview, "If he ever does go back it will be a sign of a failure on his part."
