It's one of those 'staying healthy' angles, where if he doesn't wrestle, but the other 7 guys do, his chances of winning MITB are just that...in the bank. (nyuk, nyuk, nyuk)
And if Vince gets his head shaved, this was all for nothing. Nobody is going to care that Trump shaved some guy's head. Trump looked like he'd already shaved the left side of his head tonight.