Besides playing the sports they love, why do professional athletes want to become professional athletes in the first place? Usually to make money. And in an age where celebrities are used (maybe even overused) by companies to endorse products, there’s no question that athletes expect and get a piece of that pie. Some of the most successful advertising campaigns of all time are a result of athletes becoming the faces of a company or product. In 1989, Nike aired “Bo Knows,” which features Bo Jackson (who achieved all-star status as both a Football and Baseball player) trying his hand at …