On the old Love Line Show with Adam Corolla and Dr. Drew, they would get callers all the time that were living with a beeping smoke detector and did not seem to notice or care.
Never ran into anyone like this in my own life, but based on hearing about the lives of these types of people, there is certainly a trend.
My best guess is that your solution will come in the form of bringing them new batteries, finding the smoke detector for them, and then doing the replacement yourself.
Almost certain nothing will happen if you leave it up to them.