Being told to leave a hotel bathroom light on all night sounds mysterious, but there is no universal hotel rule requiring guests to do this. The receptionist may have offered the suggestion as a simple safety measure, particularly if the room is unfamiliar or the route to the bathroom is difficult to navigate in darkness.
A bathroom light can work as a night-light when the door is left partly open. It may help guests find the bathroom without tripping over luggage, furniture, or unfamiliar steps. This can be especially useful for older travelers, children, or anyone who expects to get up during the night.
Some people also claim the light discourages cockroaches and other nocturnal pests. Cockroaches commonly avoid sudden light and retreat into shelter, but leaving a light on is not reliable pest control. Food, moisture, cracks, and hiding places matter far more, so visible insects should be reported to hotel staff rather than managed by keeping the room illuminated.
There are disadvantages too. Bright light entering the sleeping area may disturb rest, so closing the bathroom door slightly or using a small night-light may be more comfortable.
The receptionist should have explained the specific reason, particularly if the advice related to a maintenance or pest issue in that hotel. The most likely explanation, however, is improved nighttime visibility—not a secret rule every traveler must follow.
