Let us take NFL. National Football League of USA. There used to be a rule that anyone who wants to play in NFL must have gone through 4 years of college. Then the players union protested and they came to an agreement that a player must be at least 20 years of age to become a pro.
Another one is NBA. National Basketball Association of USA. Per agreement between the players union and NBA, the minimum age limit was set at 19. (LeBron James became a nationally known basketball player at the age of 14. But he has to wait until he is 19 years old to become a pro.)
I am totally against selecting under age kids in professional sports. Why?
Just stripped the childhood away from this kid.
The kid’s self esteem is tied to sports performance.
The kid cannot handle unhealthy performance pressure.
The kid will not perform for his own sake but to please his parents and not to upset the coach.
He will make more money than his friends who are not in colleges yet. So he will lose his childhood friends,
Other players in the team will have occasional alcohol parties and late-night entertainment. What will this kid do at that time? Some unscrupulous team mate will introduce the kid to all of these.
Do the clubs think there are no adult players better equipped physically and mentally than a child?
PS: I can hear someone mentioning the name of Sachin Tendulkar. He was 16 when he played for the country. He joined the IPL professional league when it started in 2008 at the age of 35. Playing for a country is different from playing in a professional league. You win a lottery (Sachin Tendulkar) once in a billion years.