9. MMA? More Popular Than Pro Wrestling
Who doesn't want to be cool? CM Punk was the coolest pro wrestler in the world when pro wrestling really wasn't very cool at all. It's not so much that he absolutely tried to be cool, but he certainly was cool. When you see something that's a personally more intriguing and certainly much cooler job to have (and you can be hired immediately), why not quit the job you currently have for the other opportunity? Once Punk had the idea that he could and should be in UFC firmly implanted in his brain (which was likely loooong before any contract was signed), still being in WWE probably seemed really dull.