I guess it depends where you are from. If you have a country with another sport that is bigger that also involves balls and feet, chances are you will give priority to the bigger sport. In Ireland, football refers to Gaelic Football generally. Soccer is more often used to distinguish between the two.

But I do find it strange that American football even includes the term 'football'. Wouldn't American handball have been more appropriate considering the ball spends 99% of the time in the players hands?