The building to the right of the sign looks like it may be a multi-unit dwelling, so it may not be clear who the culprit is. Also, many people don’t know their neighbors very well, or may have anxiety or some type of fear of social situations. In this case, they may be concerned that it may turn into a confrontation, especially if they let this go on for a month (as others have said, three minutes is my max tolerance for this). And the sign is funny and not particularly aggressive, although it may not be effective on the type of person who 1. throws their smoke detector outside instead of replacing the battery, and 2. allows it to continue beeping for a month. Maybe the OOP felt a little public shaming is in order.