It comes from the evidence. If we were to do things based on the evidence, education campaigns in public health have usually failed very miserably.
The best example I can give you is from when AIDS first came out in the 1980s. In Australia they came out with a clever campaign of a bowler, who was the Grim Reaper, throwing a bowling ball down a lane and knocking all these people over. What happened was that it had no impact on AIDS, but people stopped bowling.