This is what I have seen it used for. I can think of several times when stores' machines or power have gone out, and they have used these. I know you can write it down without the imprint, but it is my understanding that the credit card company will request the imprint if there is ever a dispute to prove the card was there. How do you prove that without an imprint?
Oh, well, doesn't really affect me. But my husband did get a new card a few weeks ago, and it still had raised numbers.