Bush's absence at RFK Stadium is the result of the fact that he is widely despised by the American public - and he despises it back.
It would be unthinkable for Bush or Cheney to make a spontaneous appearance in any large or even medium-sized American urban center. Massive security, armies of Secret Service and local police, bullet-proof SUVs and Black Hawk helicopters accompany both men on their forays into American and foreign cities. They move about like the heads of authoritarian regimes or invaders in hostile territory. Their handlers, with good reason, operate on the premise that there are many reasons for these men to be despised.
If either one of them went to a game, the stadium would go broke. There'd be so much security sitting in the stands for free, there'd be no room for paying fans. Beer sales would suffer as well.