Parents get sold an idea that their kids are learning, but this learning isn't actually verified along the way, so nobody is held accountable for making it happen.
(Sure, the kid might say they're learning and the teacher might say they're doing a great job, but can you really trust that when both parties are incentivized to say that learning is happening and penalized for saying that it's not?)
By the time the kids graduate, the learning debt is so massive that it's easier to just change the narrative. Johnny got smacked in the face by math class at college and no longer wants to be an engineer? It hurts too much to accept the truth that life could have been different if he had seriously learned math in high school. So instead it's "ah well, engineering is hard and Johnny was never really cut out for it." Or even "Johnny's engineering class is unfair."