Happy is already a state, so if you create something that's happy. . . OK, wonderful. . . but when you're in a place of distress or trauma, there are so many more directions that can go in to me. Something that's happy can only truly go in one direction, whereas with something like distress, anger, trauma, there are so many more interesting possibilities that those emotions can create.
If you look at the population of the world you have roughly 15% that will always be resisting advertising. Fifteen percent of something which has not yet been reached.