For the major sports leagues, attracting young audiences is a matter of survival. Whether the leagues like it or not, American society has crossed a Rubicon that imperils the business of traditional sports. For the first time, children ages 12 to 17 place a higher priority on being alone or spending time online rather than hanging out with friends or family, let alone tossing a baseball or shooting hoops in the driveway, according to SSRS/Luker on Trends, which conducts regular surveys about sports and society.