Yes, you grow out of it when you get your license when it's up to you to drive to 5 games a week and you release it's a waste of productive time.
1. In most areas, this "most popular sport among American kids" (soccer) is almost exclusively played by kids who are dragged to practices and games by their parents. You see hordes of these kids playing soccer on any given Saturday morning in suburban areas all over the U.S.
2. I see city kids (and adults) playing basketball on playgrounds at all hours of the day and night. I see kids playing street hockey in suburban areas and ice hockey on frozen ponds out in the country. The numbers are definitely declining, but I've seen kids playing football and baseball on their own in parks and playgrounds regularly over the years. But outside of areas with heavy immigrant populations, I've hardly ever seen kids playing soccer on their own without their parents around.
I think that says a lot about why soccer has had such a hard time growing in popularity in the U.S. at the adult level. Most kids who play soccer really don't love to play it.