Parents and/or students make the conscious decision to go into debt believing it's a good idea because the student will have a college degree and statistically make more money throughout his or her career. It's an investment that they make.
Some parents and students choose not to go into debt. Some like me, chose to attend a college that was affordable to where I wouldn't need to take out a loan. I worked my way through college. Some don't choose to go to college at all and take a different path. They aren't willing to invest money into a four-year degree, or just can't for one reason or another.
What these Dems are telling everyone to do, is to take all those people who chose not to spend money for college or paid for it on their own by choosing a non-expensive college, and have them help pay for the college educations of other people. The very people who voluntarily went into debt so they could "better," themselves. So Dems want to tax other people so they can help these people make more money in life.
I hope the absurdity of this, sinks in.