“Going through the college admissions process once can be emotionally wrenching — but more than a third of students choose do it again. A 2015 report by the National Student Clearinghouse Research Center found that more than a third of college students transfer and that nearly half of those do it more than once.” …
Missing are perfectly benign reasons that are common. Example would be someone who starts at community college, possibly attending more than one, then transfers to a university to finish a BA or BS.