The academy system would build their own facilities, pay their own bills, and not eat up such a portion of school budgets. If there were a football league where the Ann Arbor Wolverines played the Columbus Buckeyes and there was no attachment to either of the schools, but everything else was exactly the same, fine. Operate like a business. High schools I am a bit more ambivalent on, as they are conceivably accessible to everyone, but even there, the football fields, gyms, baseball fields, tracks.... that's money that could be put to better use at a school.
But the whole fact of the matter is, with the exception of maybe hockey, any kid with athletic prowess gets asked "where are you going to play in college?" Screw that. Colleges have their role, and creating, sustaining athletic pipe dreams is not one of them. If the pro leagues want a development system, they can develop it and look after it. Colleges should not be using the resources they do for facilities etc. that are only accessible by less than 2% of the student body.
If you can play, and someone wants you to play for them, and possibly pay you, great. But your SAT score or whether you missed 3rd period Science should not factor into it, nor should you have to go through a calculus charade just because you can get to a QB.
Sports academies can handle sports, let schools do what they are supposed to do.
Little League isn't tied to a school. No need to go further than that.
The second part is the shortest, so I'll address that first: the fact that Little League isn't tied to a school doesn't matter, it's the same model: Kids who live in a place, playing kids who live in another place. The kids need things like uniforms and orange slices to do that, and because some amount of people want to watch the games they play and are willing to contribute some money to fund that endeavor... all teams pay for a combination of what they deem "necessary" to compete vs what they can afford.
The only difference is dollar amounts. (And Little League even has a TV contract roughly the same size as the Big East!)
The reason the US doesn't have an academy system** isn't on the colleges; it's on the PROS.
The academy system is just straight up BETTER for developing players than what the NHL, NBA, MLB and NFL, which is essentially NOTHING.
There's no reason for those leagues to take on the expense of development because with only 30-32 teams in the best leagues in the world at those sports, they can simply take the Top 0.01% of players who
develop themselves in into elite players.
There's well more than 25,000 college football players. The NFL drafts 224 per year. (.0090%)
There's 500,000 high school and college baseball players. MLB drafts 600 per year (.0012%), plus the foreign players not subject to the draft.
There's 5000 college basketball players, the NBA drafts 60 players (.0118%) plus the rest of the world contributing players.
There's 8000 Junior Hockey/NCAA players, the NHL drafts 224 (.028%) plus the rest of the world)
Soccer on the other hand, totally DOES need to create players, because England alone has like 760 pro teams. MLS relied on the "North American Draft system" and it got them no where.
(That was my ** from before: MLS has an academy system now, because it was totally necessary to raise the quality of American players for US Soccer, and for MLS teams to export players from their academies to better leagues for cash).
If you're a male college soccer player, it's too late for you to be a US National Team player.
But pretend for a second that all the pro teams in NFL, MLB, NBA and NHL actually had an academy system. What would change in college sports? From a business sense, NOTHING.
There'd be less elite players in the NCAA. That's it. No one would care... because there's ALREADY less elite players in the NCAA than before. NBA Lottery picks rarely play 3+ years of college basketball anymore anyway. Larry Bird and Michael Jordan played 3 years of NCAA basketball, and LeBron and Kobe played NONE.
College sports fans are NOT watching for WHO THE PLAYERS ARE. They're watching because of the school they went to/root for, and they want THEIR PLAYERS to be better than the OTHER SCHOOL'S PLAYERS. That's it.