The bars in this figure shows per-student sending on pubic higher education by state and local government from all sources of funding, with the lower blue part of the bar showing government spending and the upper green part of the bar showing spending based on tuition revenue from students. The red line shows enrollments in public colleges, which have gone flat or even declined a little since the Great Recession.
The reliance on tuition for state public education varies wildly across states, with less than 15% of total spending on public higher ed coming from tuition in Wyoming and California, and 70% or more of total spending on public higher education coming from tuition in Michigan, Colorado, Pennsylvania, Delaware, New Hampshire, and Vermont.
There are lots of issues in play here: competing priorities for state and local spending, rising costs of higher education, the returns from higher education that encourage students (and their families) to pay for it, and so on. For the moment, I'll just say that it doesn't seem like a coincidence that the tuition share of public higher education costs is rising at the same time that enrollment levels are flat or declining.