A single institution might manage residence halls, academic classrooms, research laboratories, athletic facilities, maintenance buildings, and administrative offices, each with different access requirements and different groups of people cycling through them.
Campus security management across that kind of footprint means dealing with keys that serve completely different purposes, from a building master used by facilities staff to a single-room key issued to a graduate student for one semester. The variety of use cases is something that informal key management practices were never designed to handle well, and as campuses grow, that gap tends to get wider.
The people who need key access on a university campus are also constantly changing in ways that most other environments do not experience. Adjunct faculty come and go by semester, sometimes teaching at multiple institutions simultaneously. Graduate researchers may be assigned lab space for one academic year and need different access the next.
Every personnel change represents a change in who should have access to what, and in most campus environments, managing that change is more of an informal process than a controlled one.