This is a good point, though for most people, valuable skills are often "dry" and undesirable like plumbing, so someone who was really passionate might've persevered on his own anyways. Even if academia has the merit of making you persevere through a class you wouldn't have on your own, it's not efficient; Most of the classes colleges require from you to just graduate aren't "you-will-actually-need-this-later-in-life" classes and are just filler classes.

Front-loading on dry subjects also has the downside of scaring away people who would've otherwise done well given a different path of learning.

The timing of when you learn some things is also important; it matters not if you learned software architecture in college only to have all the knowledge become obsolete by the time you really need that skill - you'd have to review or worse relearn it by yourself all over again.