That's the point. Since so many sports are competing for "player attention", people may commit to the "wrong" sport early on, be decent, and then top out at an age where it's too late (in terms of going pro) to switch to a sport they may have been great at.

In a hypothetical world where every kid plays only soccer, every potentially great soccer player has been practicing the sport from an early age. In a world with 10 competing sports, some potentially great soccer players might have be playing baseball or basketball from a young age up into their late teens.