An excellent point.
When I was a child, we just grabbed our mitts/bats/balls/frisbees/whatever and went out to play with our peers and came home when it was dark/raining/time for dinner.
Over the last 30 years or so, it seems that (not that such things didn't exist 30+ years ago) in most places it's difficult to engage in sports without an organized group/league, especially in places where greenspace isn't within walking/biking distance.
As such, most kids need adults to get them to/from sports and there's not very much in the way of pick-up games[0] and the like.
The lack of unstructured sport leaves many kids out of sports (given that parents need to spend time and money to get their kids involved and to/from such activities)
N.B.: The above is definitely a US-centric viewpoint.