Generally speaking, brand awareness is a good thing, and if you’re an athlete, and you’re instantly recognizable to people off the street, some of whom may not even necessarily be fans of your sport, that’s typically not bad, either.
But if an athlete has goals for himself regarding how he’s perceived, both in the short term (in regard to his talent, for example, or other characteristics that define who he is as a player) or in the long-term (how he eventually fits into the pantheon of players who preceded him), just having people know who you are isn’t enough.
There’s no better example of this than Tony Romo.