Professional athletes and sports players weren't allowed to bet on them or upon the game they play. This is done to have them self control, because once they start placing bets on them, it'll be the beginning to play for his/her favour. Finally his game game will be much based on personal financial gain which is not good while representing a team or a country. For this reason professional players weren't allowed to make bets, but these days there are chances of professionals making bets using the anonymous betting opportunities.