I think it's to communicate that even if you think it's not that bad, it's never good: A single beer every month probably won't kill you, but there is a non-zer

I think it's to communicate that even if you think it's not that bad, it's never good: A single beer every month probably won't kill you, but there is a non-zero increase in risk. By definition, any amount is a danger. I believe that kind of communication intends to combat the more laissez faire "a beer here and there won't kill you," which glosses over the fact that, yeah, it probably won't, but it's also not without statistical risk. Getting rid of that attitude reduces the risk of alcohol-related health complications across the population as a whole.