Plenty of people know. They are demons. Unfortunately there are many who don't believe what the bible says about demons and so think they are something other than what they are. Beings who hate people and hate God. The sooner you realize this the sooner you'll understand why the world is the way it is right now.
That's quite possibly correct (though I'm not willing to close the book on that conclusion just yet). And that's why we need to understand what we're dealing with.
If a kid says, "Dad, I think there's a pack of wolves at the door." It's important that we check it out.
It may be the neighbor's 3 friendly chihuahuas or it might be a pack of vicious feral dogs. It helps to know the difference.