@ determined2300 I did not mean to imply that students don’t eventually graduate because they do. The six year graduation rate is somewhere around 80%. One of the reasons for this is that many students do co-ops which are semester long (or longer) jobs in the students field. Students will often do more than one during their school career. Yes, it takes longer to graduate, but you gain valuable experience and oftentimes a job. These experiences are not required, but are very popular.
Secondly, as stated above, many majors are time consuming requiring more than 120 credits. My D started out as a BME major which requires something like 133 credits. It would be very hard to complete that degree on time without AP credits. (she changed because she realized that would be a terrible major for pre med)