"Free" education is the only thing that separates us from a dystopian society of social immobility. And hence people in US defend it.
I came from poor background and the fact that Uni education is free allowed me to, first of all, receive it, and also take risks that I wouldn't be able to do if I had to repay a 100k+ loan. These kinds of risks are what in essence allow social class movement, otherwise, we are talking about more comfortable wage-slavery.
On the other hand, belief in higher education wanes, people question if degrees like philosophy are "useful" (whatever that means) and then question why voters have no critical thinking to decide their own future.
I would love to see if there is historical data supporting my intuitive belief that free access to higher education made significant differences in the advancement of otherwise similar nations. USA is throwing its education down the drain and the decay is already visible.