If it’s a pressure cooker (and that’s a GREAT analogy), then we don’t necessarily want the lid coming off under pressure. Because that would be very violent! Better to release the pressure in a quick, but controlled manner. Sort of a big “whoosh”!
I use a pressure cooker frequently. One definitely wants to take the lid off with car. Right now the pressure is at the danger point. If I am in a rush and I know the stuff in it is cooked, after I take of the fire I’ll remove the little nozzle thingie (what is it called?) from the steam vent. It’s not like taking the lid off under pressure would not be pleasant.