They also know exactly what they are doing. Probably preying on college students that are broke and don't have the time, money, or legal knowledge to go after them via legal means.

And if they did try something themselves like withholding rent, there's a good chance they won't have followed all of the prerequisite steps and documentation necessary and will threaten eviction, which will essentially prevent them from renting another apartment in the future with that kind of mark on their record.