A large part of that is due to a combination of severe cuts to subsidies which were much more abundantly provided by federal, state, and local governments and large changes in society which resulted in a much greater proportion of the population attending college than before along with a rejection of extremely selective admissions(CCNY/CUNY before 1969) or wide-ranging mandated weed-out policies for academically unmotivated and/or under prepared students in public institutions with open-admission policies for in-state students.
It may also be a possible coincidence that this was also around the same time public K-12 funding started to get cut substantially to the point the deleterious effects of this neglect became quite apparent by the late '70s and 1980’s.
This issue didn’t really exist in public universities before the mid '70s because it was free or extremely nominal cost for in-state/in-city residents. And they were not all fall-back options as most are viewed nowadays.
For instance, when General Colin Powell opted to attend CCNY over NYU in the '50’s, that wasn’t only due to cost…but also because at the time he attended, CCNY was considered a much more academically elite institution than NYU*. And back then, it was free for city residents and nominal cost for everyone else.
The flipside, however, was either one risked being part of the substantial proportion(sometimes as high as 50%) of in-state students who were “weeded out” in an open admission system or if admission was selective, competition to get in was extremely keen as there were so many applicants in relation to available seats and the academic level set high enough that there was a bit of a “CCNY/CUNY or bust” attitude among many parents and academically high achieving students.
Especially those who were deterred from Ivies/elite private Us due to higher costs(no FA and not too many scholarships back then) and/or discriminatory admission policies (Strong disinclination by Ivy/peer private colleges in this period from admitting too many students who were Jewish, Eastern/Southern Europeans, and other “undesirables” who weren’t upper/upper-middle class and WASP in that period).
Incidentally, I faced the same issue when I was applying to colleges as it would have cost me more to attend my local public colleges right when they were at their nadir in terms of academic reputation/rigor. This was only confirmed when several HS classmates who started at a few local 4-year public colleges because of poor HS GPAs or parents who believed “all colleges are the same”*** ended up voting with their feet after a year or two by transferring out to elite private LACs/universities like Reed, CMU, and Columbia.
- A few older friends and neighbors who attended NYU back then were quite frank about the fact they attended because they were rejected from CCNY/CUNY and that NYU was widely considered an academic safety for many tri-state area students during the '40s till the late '60s.
** And after the end of the '90s as well with the CUNY 4-year colleges when they started an initiative to move towards no longer directly admitting remedial students to the 4-year colleges.
*** The flipside to the Ivy/peer elite or bust mentality often discussed here on CC and IMO…equally nonsensical.