Because most of the kids if they stay active in sports will usually gravitate toward one of the more popular US sports.I wonder why that is. I know lots of folks who have their kids in youth soccer, some devotedly so. It seems to dominate some of their lives. It seems to be one of the more popular youth sports, if not the most. But few kids actually go on to play soccer at much higher levels.
Maybe it's popular because it's cheap. Don't need much in the way gear. Also, kids get lots of exercise.
The US sports have a greater popularity in other countries than Soccer has here because of how huge the US influence is on the rest of the world. The exception to that would be American football just because of the number of players something like that takes. In basketball, you have 5 players that play both offense and defense. In American football, you have 11 players that would be starters on one side of the ball and another 11 on the other side, not to mention special teams. I do not think you will ever see soccer in the US be anywhere near what it is in the rest of the world. It will take generations of Ravid fans for it to take that kind of hold.