I suspect a few of the BLM signs are like fake home Brinks or ADT signs used as a deterrence. It’s not hooked up but the signs throw off the bad guys.
That’s funny you mention that. I never considered that people do that until a few months ago I had to drop something off at a neighbors 3 doors up. They have a screen door that you walk into and then the front door is a few feet away....a Florida thing. So after dropping off the papers, I went to leave and I couldn’t open the door no matter what I did. Thank God a neighbor was outside and was able to open the door. We all thought it was part of the security system they had as they had a sign. I saw her later and said your security system works. I could not open your screen door from inside. She said, “oh that? No that sign is fake and the door just needs some oil.” That threw me as I never considered people would do that. Lol.