Not to be too picky, but the gambling firms don't have a better grasp of the odds. In fact, they often try to avoid taking sides. They look to set the odds so that there are more or less the same volume of bets on both sides. Then they add a small fee (aka rake, vig or vigorish) which is generally the source of their profits.<p>Some gambling operations like the paramutual betting pool at horse tracks don't even promise any odds. The odds shift as the bets come in and the prize pool is just split up between all bettors equally -- after about 17% has been subtracted to pay for track.