The reason to force young people to buy health insurance under the Affordable Care Act (ACA) was because they are an easy profit center. They won't use much in the early years but they will when they are old, when a new generation of young people will be forced to pay.
It hasn't really worked out that way. While emergency room visits did go down slightly, visits were instead done more in an office for the difference, the cost of mental illness ER visits in this age group increased "significantly," as did diseases of the circulatory system, according to a paper in Annals of Emergency Medicine.