@pastanaga - Well, sometimes it's not about making an immediate statement, but about getting into the community consciousness. If people see ads demonstrating that drunk driving is bad over and over, they might simply take the message on board without thinking about it.
And some social marketing campaigns do make a direct difference as well. I remember seeing one on social media where ads in a shopping mall were designed to look like a normal child from an adult's height, and an abused child at a child's height and there was a number that only children could see that they could call if they were in trouble.
That's the kind of thing that could save a life if someone saw it who really needed it, and it managed to do good without alerting the abusers to what was going on.