Several CSUs (CPP, CSUFresno, CSUSB, CSUB, CSUStanislaus) have four year graduation pledges (where students can get priority registration for needed courses, or free tuition for any additional semesters needed). However, students cannot need remedial courses, must take full course loads following their majors’ course plans, cannot fail courses, and cannot change majors. It is likely that most students are unable or unwilling to meet these requirements – the relatively low selectivity of most CSUs means that many students do need remedial courses or are unable to handle or pass full course loads.
CPSLO does have a lower four year graduation rate than other schools of similar selectivity (47%, versus 68% at UCI). I have not seen a good explanation as to whether it is something that is the school’s fault (meaning not enough space in required courses), student factors (needing remedial courses, changing majors, not taking full course loads, not wanting to take the required course at 8am), or innocuous reasons (co-op jobs). CPSLO’s graduation rates are rising, though (perhaps in part due to higher admission selectivity and higher costs creating incentive to graduate quickly): http://content-calpoly-edu.s3.amazonaws.com/ir/1/publications_reports/ret_grad/persist-ftf-1314.pdf