I guess they can work when no one knows about you. After a certain point, there must be diminishing returns in comparison to just your current customers recommending your product to their friends.
I'd imagine so, yeah. Like, I can't imagine what value French's gets out of running mustard advertisements as an example. Feels like some of these companies have entire marketing teams whose main job is to justify their own existence because upper management hasn't yet figured out that they're not going to reach anybody who's never heard of mustard before.