Conspicuous by (one's) absence humorous idiom
People notice someone's absence because they are supposed to be there.
It's his own father's funeral. Of course he's conspicuous by his absence!
A: "Hmm, I wonder if anyone notices if I didn't show up to class today." B: "Dude, you are the class monitor. You will always be conspicuous by your absence."
Bad people but they are still rich or wealthy.
Fairy tales have a lot of the devil looks after his own but in the end they are still punished.