Sure, but under the scenario I outlined no one has college debt. In such a world what is the drawback?

The DOE just released a study showing that half of all student loan borrowers are effectively unable to pay back their debt. That is quite a high number...

America’s Student Debt Problem Is Much Bigger Than Anybody Realized

The Department of Education recently released a memo admitting that repayment rates on student loans have been grossly exaggerated. Data from 99.8% of schools across the country has been manipulated to cover up growing problems with the $1.3 trillion in outstanding student loans. New calculations show that more than half of all borrowers from 1,000 different institutions have defaulted on or not paid back a single dollar of their loans over the last seven years.

https://www.wsj.com/articles/student-debt-payback-far-worse-than-believed-1484777880
http://www.zerohedge.com/news/2017-02-02/america%E2%80%99s-student-debt-problem-much-bigger-anybody-realized

The government needs to leave the university scene.
As soon as they try to make it "cheaper" for all, the prices skyrocket. As they bring in more grants, more loan's, ect all it ends up doing is the colleges raise the price of tuition.

Look at the prices of tuition historically, then look at the prices of tuition once the government decided it needed to "step in" and make tuition more affordable for all. Prices have since been on a constant rise.

What is the government idea of a solution? More intervention. More loans, more grants, ect. All that will do is make Universities know they have more guaranteed money coming and thus raise tuition again. Students go into more debt again.

Uh-oh

Half of college students think their loans will be forgiven

According to a survey of 500 current college students conducted by LendEDU, a private firm that connects students and their families with student loans and loan refinancing, 49.8 percent believe they would be able to receive federal forgiveness on their student loans after graduation.

With maybe 14 percent of the American workforce in a public service job, the actual numbers of those who may qualify for student loan forgiveness or discharge is maybe below 10 percent.

The biggest problem in my experience is that people don't just take out loans for tuition. They take out huge loans to pay for food, housing so that they can live very comfortably (have money for going out drinking/partying, etc). There is a lifestyle expectation that people are willing to pile on more debt while they pursue a degree that provides little chance at paying it back.

Interesting fact, student loans are much more a women thing, 2/3 of all student loan debt owned by women.

KANSAS CITY, Mo. -- Research released Monday shows women are saddled with nearly two-thirds of the nation's $1.3-trillion student loan debt... The report says it takes women a lot longer to pay off their student loans, compared to men in the same situation.

http://fortune.com/2017/05/24/women-student-loan-debt-study/
http://fox4kc.com/2017/05/22/women-own-nearly-two-thirds-of-nations-student-loan-debt/

A look back at the Obama presidency:

• Federal student loan debt went up from $154.9 billion in 2009 to $1.1 trillion by the end of 2017
• Borrowers have been flocking toward various loan forgiveness programs... The report shows that the direct loan program went from a $25 billion surplus in 2012 to less than $5 billion by 2015. A separate report says that this program ran a $36 billion deficit last year, up from $8.4 billion in 2016.

https://www.investors.com/politics/editorials/student-loans-will-cost-taxpayers-36-billion-thanks-obama/

The US obsession with enemies reflected in it defense spending has a huge cost on the rest of it's essential spending, students among others are essentially subsidising the arms industry   

Context: military spending as a proportion of GDP went down dramatically over the last decades, while social spending rose and is now 5x higher than military. 

http://www.pewresearch.org/fact-tank/2017/04/04/what-does-the-federal-government-spend-your-tax-dollars-on-social-insurance-programs-mostly/

These taxpayer-financed systems can work nicely but you need strict rationing to avoid cost explosion. A good example would be to limit taxpayer-funding to the top 1% or maybe 10% of the students with the best grades.

If people don't pay their loans, the principal amount will increase and increase over time. Some private lenders will resell the loans for a lower price to a speculator. Government loans will ultimately run a loss and the taxpayer has to pay the rest.