I think the mistake you're making is you assume it's the skills (gained and later forgotten) that the employers care about, but in reality the college degree is just a filter, not unlike an IQ test. Sure, it sucks that it takes four years and costs $100k, but hey it's not the employers that pay so what do they care. (That's why degrees are less important for engineers, since you can filter eng candidates by asking them a few coding questions.)
(Not that this makes the situation any less deplorable.)
(Not that this makes the situation any less deplorable.)