The leagues have basically outsourced their minor-league systems to colleges, which spend hundreds of millions developing talent and separating the wheat from the chaff. If college players sustain career-ending injuries before they make a nickel, that's their tough luck. Last year the best defensive player in college football, the University of South Carolina's 20-year-old Jadeveon Clowney, took out an insurance policy on future earnings because he was barred from entering the NFL and understood the financial risks of getting hurt during his third year of college.
The vast majority of collegiate athletes will never play professionally, of course, and even most elite athletes need more time to develop their skills before going pro. But not all. Before the NBA increased its minimum age to 19, LeBron James, Dwight Howard, Kobe Bryant and Kevin Garnett all had immediate success as 18-year-old rookies and have long been among the best players in the NBA.
The players' union was wrong to accept the higher age restriction and should resist any push by new NBA Commissioner Adam Silver to raise it further. Instead, the union should insist that the NBA put more money into its development league to make it a more attractive alternative to high school players with no interest in college.
The NFL has no developmental league, but an independent league (FXFL) is beginning this fall in four cities and could grow into the minor league system the NFL needs. Most 18-year-olds are not ready to play for a college football team, no less a professional team, but a few may be and others are ready at 19 or 20.
It may well be that most 18-year-olds are better off going to college, even if they don't end up earning diploma. But the choice should be theirs to make. An 18-year-old who has the talent to work for a professional sports team should be treated no differently from one who has the talent to work for a technology company. The decision of whether to attend college and for how long should be the individual's.