(If you don’t agree with my “acting under fire” example – I admit it’s not bulletproof – consider moves like Oftener Right or Eager to Know. If you apply that move every time someone takes or offers advice, in every single conversation, you’ll end up in a quagmire. Instead, you apply it to mark a moment when something seems meaningful and you’d like to see it feature later, as a way of signaling this to the other players, and the +1 helps it “stick”, so we don’t forget later.)
(Same goes for the way most people use the “harm move” – it’s not rolled every time someone’s hurt, but when we want to “zoom in” on that moment and lend it some extra weight.)