A few CSUs had four year pledge programs (two year pledge for transfers). These are now expanding to more CSU campuses and majors under the name “California Promise” (which is not limited to scholarship or honors students, but can exclude those needing remedial courses).
The conditions include be taking full course loads and following your major’s course plan, not needing remedial courses, etc… (Doing these things means high probability of on time graduation anyway.)
But four year graduation rates are still low, probably because of other reasons like students not being able to take full course loads because they need to work lots of hours, or are not that strong students to being with.