There apparently are some backward-thinking colleges, departments, or faculty members who believe that old tests and test questions should be kept “secret”, so that they can be reused. They may consider using old tests and test questions as study tools to be cheating. But that may not prevent the existence of unauthorized test banks in fraternities and elsewhere, or other “leaks” of old tests and test questions.
This problem is not limited to colleges. It happens in high schools as well. A recent high profile case involved the radiology board exams.
Some colleges, departments, and faculty members make old tests and their solutions public, ensuring that there is no unequal access to them.