The cause (for both) is that we, as a a society, have decided that a service provided by the private sector is a need for all of us, regardless of our personal circumstance. To that end we, as a society, have further decided that we shall use government resources (read: $$$) to provide support for those who are unable to afford what they need.

As mentioned, supply and demand become decoupled from one another because the consumer and the payor are not the same entities. It does no good to make moral judgements about people who make bad decisions about what student loans they take out to fund the dreams of a future that might not become a reality, or about medical providers who are more than happy to make every service available for every patient regardless of the cost. We, the people, have decided that these services should be available to all who need them, and the individual failures along the way are (or should be) obvious outcomes.

This will continue, unabated, until one of two things happens:

1) We decide that these services are not actually a need, cut off the free money faucet, and are willing to endure a couple of decades of absolute carnage in the middle class and massive upheaval in the national economy while the markets for medicine and education sort themselves out. Not to mention what happens in the employment market generally when the supply of college educated 20-somethings dries up, or

2) Accept that things deemed as needs require a viable more-or-less free public sector option. e.g. the public school system. Public schools, as much as they are not perfect and tend to hemorrhage money, do a generally fabulous job of turning out legions of young adults eminently qualified for employment in an industrial society. If modern society requires more and more of us to be educated beyond what we cover in K-12, the perhaps it's time for public education to go beyond that.