It is of responsibility and discretion of the hotel staff to search and expel those who overstayed; and it is not the responsibility of the residents or the guests of the hotel.
Circumstantially, it could be dangerous, and probably, dark and psychologically damaging, to be busy bodies.
You can not force people to be butchers, or executioners. It is not justified to make people to do immoral activities. There are many serious consequences, including psychological, in engaging in immoral activities.
Informing illegal activities could be merely a voluntary, and a moral choice; because, those who disclose information are more like to face security, and or other forms of risks, including, psychological distress.
Many people would perceive that they have more pressing things in their lives than keeping an eye an on people’s visa status.
It can not be morally justified that providing shelter, food, etc to desperate is wrong.
Therefore, for some, if not all, of the foregoing reasons, any attempt to prosecute someone for harbouring illegal immigrants would fail in an uncorrupted court of justice.
Therefore, government would fail to force people into providing information about illegal immigrants.