my social theory is simple: economics.
What can be cheaper than kicking a ball( any any object approximating a ball) around any opening area one can find. Notice how expensive other sports can be like basket ball(court/hoops needed) football: pads/helmets/shows & goal posts/field etc. Baseball: gear/ shows etc... since thats all they play since they can walk.
You know the saying: practice makes perfect.

That's why Germany ,Spain, Netherland , Italy , England .............etc . are some of the best team in the world
and El Salvador,Guatemala, Sudan ,Ethiopia , Haiti ........................
........................
.........etc . are some of the worst
