Like goatsi said below, it makes it much harder to duplicate than a metal key, and tracks the times and fob IDs of everyone using it to get in the building. Ins

Like goatsi said below, it makes it much harder to duplicate than a metal key, and tracks the times and fob IDs of everyone using it to get in the building. Instead of being able to run to Home Depot and get a key copy for $3 that you can hand out to whomever you're lending the apartment to, you'd need to copy your fob or lend them yours. This makes it fairly trivial to lock a single fob out, and there are timestamps that can be corroborated with the camera in the building lobby, to see who was using the fob to get into the building. Of course, cursory Googling when they were handed out shows that it's not that difficult to clone the model of key they handed out, but it's still a big 'win' over everyone having the same key.