You know the old cliché about not knowing the meaning of fear? Well, PCs know the meaning of fear, all right. Just tell them that a treasure chest "looks like it is not trapped", and watch them do everything they can to avoid being within 60 feet of it when they open it.
What PCs don't know the meaning of is subtlety.
GM: Right, let's not waste any more time. Luke, Yoda, you're still on Dagobah.
Luke: Holy poop, Darth Vader thinks I killed his son, but I am his son... this is super messed up!
Yoda: Worse, it is. Summoned Vader's attention to the tree, you did. He saw your actions, as you have long been able to sense his.
Yoda: You must learn to keep him out of your mind. A Jedi skill I will teach you, called Occlumency!
Luke: Why didn't Obi-Wan tell me the truth?
Yoda: Thought he was helping you, Obi-Wan was.
Luke: This is not helping me!
Luke: My dad's the most evil person in the Galaxy. He can read my mind. And I'm still the only one who can stop him. This is heavy.
Yoda: Stop him, you can, but many paths there are. The Jedi way is subtlety, remember, not aggression.
Luke: So... a subtle shiv to the ribs or something?