I rarely show my cards, I only do it if I feel I can manipulate a villain's approach in future hands. Showing you fold AK tptk to a stupid open shove tells him that he can push me off tptk by open shoving. So maybe next time he thinks I have tptk he open shoves a wider range, making my tptk a much stronger hand.
Likewise, maybe I show a bluff because I think there's a good chance it will tilt villain into making mistakes.
I only show my hand if I have a good reason to.