I remember, in the dark ages when I was young, that candy bars were innocent unless proven guilty (by scanning the ingredients.) Those days are over. Now that products are available with a hechsher, and we know more about what can go wrong, we no longer rely on that.
btw, I saw a new Hershey’s products several months ago, and their website indicated that it was kosher, and it was noted on the label shortly thereafter. but don’t try this at home!