#1 Could hurt the WWE : Punk's MMA losses hurt his tough guy image.
When CM Punk first made his debut for the short-lived WWE revival of Extreme Championship Wrestling, he certainly looked the part of an ECW wrestler. Even better, he seemed to walk the walk as well as talk the talk. Punk claimed to be a 'master' of Muay Thai and Gracie Ju Jitsu.
This led to his using a lot of strikes against his opponents, and his Anaconda Vice submission hold. He also borrowed the Go to Sleep from Hideo Itami. Part of Punk's appeal was the fact that he was considered to be a legitimate 'bad ass' street fighter.
This image would hold for most of Punk's wrestling career. However, when he stepped into the Octagon for his first MMA fight, his lack of experience was woefully apparent.
Now that he can no longer push the tough guy card, he may have hurt his credibility with fans and prove to be a detriment to the WWE.