Love letter for lazy arsonists

I'm sure this sign is posted to satisfy some sort of law but I'm a little confused. If I were someone who had a key to this building, wouldn't I already know that the fire protection is out of service? If I had a key and I didn't know and a fire started inside the building that I couldn't put out, I'm pretty sure I wouldn't wait around to see if the fire protection could put it out. If I were someone looking to break in to this building, I don't think I'd care about the state of the automatic sprinklers. And if I were a policewoman and/or firewoman I'm pretty sure I'd have to run into the burning building to save someone even if the sprinklers were out of service.

So all I can figure is that this is a love letter for arsonists. And a lazy arsonist at that.