Why do American schools focus so much on athletics/sports?

Being an international student, I have noticed that almost all American schools focus a lot on its athletic programs. Is this because sports like football are a part of American culture/heritage? Or is it because schools actually truly believe that playing on a team builds essential life and problem solving skills that can prepare students for the future? I have noticed at some schools, a persons athletic achievements and abilities are glorified to the point where it becomes the only manifestation of success in the eyes of faculty and other students alike. Whereas in my old school, a students grades are the only indicator of success.