I am a student and where I live most student housing has an app to open the door instead of a normal key. My current place used Bluetooth, the previous one was even more inconvenient because it used NFC. It sucks, and if you accidentally forget your phone at home you're fucked, but the landlords do it because it lets them block old tenants from entering without having to switch the locks.
They do. But the apartment complex gets a nice little kickback, especially since an app for unlocking your front door is one that has at least a plausible argument for having your location, which means a whole bunch of location data that can be mined/sold/both.