In many American sports the serious development now happens in club programs that charge fees. School teams increasingly select from players who already trained elsewhere.
Development moved outside the school
School seasons are short. A club season runs most of the year, with more coaching hours, more games and more contact with the people who evaluate players.
A student who plays only the school season arrives each year against opponents who have been playing continuously, and the gap widens with every season rather than closing.
Coaches are not selecting by wealth. They are selecting by demonstrated skill, which by that age has been substantially determined by who could afford year-round training.
The listed fee is a fraction of the cost
Beyond dues there are uniforms, equipment, tournament entry, hotel rooms, gas and meals on the road, plus the parental time to drive to all of it.
Travel is the item that most often ends participation, because it requires an adult with a car and a free weekend, which many households cannot supply regardless of dues.
Scholarship funds usually cover dues and not travel, which is why aid programs can be generous and still fail to change who is actually on the roster.
Recruitment follows the tournaments
College coaches evaluate efficiently by attending events where many teams play in one place. Those events are club events, held on weekends, often far from home.
A player absent from that circuit is not evaluated. Her school performance may be excellent and simply unobserved, and unobserved is indistinguishable from unremarkable at that stage.
Early specialization is a consequence, not a choice
Because club seasons overlap, playing two sports becomes impractical, and families are pushed to commit a child to one sport well before anyone can tell where she will be best.
The overuse risk from that concentration is well recognized in sports medicine, and a physician or athletic trainer is the person to consult about a specific young athlete's load.
What changes the pattern
Recreational leagues that continue through high school keep players developing without the travel structure, and they preserve a route back for a student whose family circumstances change.
Some districts and community programs run low-cost offseason training in school facilities, which is the single intervention that most directly substitutes for what club fees buy.
Where neither exists, the roster at a public high school ends up reflecting household income more closely than most people in the building would guess.