I disagree. I think what you're saying are "a lot of exceptions" are primarily going to be in what are historically referred to as "revenue sports" in the US -- football & basketball -- and also in individual sports where personal marketing is key to financial success (e.g. sponsorships).

I don't see it as unexpected for there to be big egos and boisterous personalities in sports where individuals are hugely rewarded for personal success. From an athlete's point of view, creating a commercial persona is almost as important as performing at their best on the field/track/bike/pool/course/etc.