In the U.S., this is due to the fact that employers practically may not use proficiency exams; since they are prevented from testing for actual proficiency, they must use a proxy, and a college degree is a decent proxy for 'reasonably educated enough, exposed to enough general knowledge, knows how to function in a group.'
I don't think that class really enters into it.
> the fact that educational debt in America can never be voided through bankruptcy seems like a conscious systemic decision to create debt slaves.
More that without the inability to discharge it in bankruptcy interest rates for student loans would need to be sky-high: the smart move for anyone graduating at 22 would be to immediately declare bankruptcy when all he would have is debt and no assets.