I wouldn't say he doesn't need it then. Just because you don't know what something is used for, does not mean that you wouldn't have a use for it. He could have something he is trying to accomplish, but does not have an idea of how, and roughing spray could be the perfect solution.
Also, it can be used for a lot more than just a few gaffed decks, but those are what it is generally used for.
there are also some packet effects that benefit from said product.