Cheerleaders in Baseball

Cheerleaders, aka scantily clad young women, are used to sell everything, from the Dallas Cowboys, to the 49ers, to prescription medication. The Atlanta Braves do indeed have girls who dance in short shorts on top of the dugouts a few innings per game, but as far as I know, they are unique. The Red Sox have nothing. Why are cheerleaders the exception in baseball, but the rule in all other American sports?