The question isn't why WE call football, football.
The real question should be why do Americans call American Football, Football - when it clearly isn't. Barely any use of the foot, and the fact that the ball isn't a ball.
It's more like Rugby, only with protection and rediculous tights.
American Rugby would be a better name.
Better yet "American Sissy Padded Gotta Wear A Helmet Cos Im A Pussy Rugby". Hehehehehe.
Gotsta ruffle a few feathers with that one.......