We hope the social redistribution that would have to be there to help those that fail, and those employed to teach them, is less expensive than every citizen forced to sacrifice 8 years of prime life time and tens of thousands of dollars.
Because that is how we are redistributing from successful people to not-successful ones right now.
You can't make people more knowledgeable by not attempting to measure their knowledge. You can maybe try to improve things for subsequent generations. But issuing a false credential won't solve the problem.
Remedial classes. Or, realistically, unskilled labor.
Like, what do we do with these kids now? The same thing, except after we’ve saddled them with a meaningless diploma and a pile of debt.