I see this sentiment a lot, but honestly I think it would actually do the reverse of what people suggest. “Common sense” isnt really some inherit knowledge that everyone not stupid knows, its actually just stuff that we expect everyone to have learned at some point, presumably in fairly early childhood. But learning stuff requires being taught, and its easy enough for something to just have never come up for someone when they were a kid, because there are so many things to know. Having an explicit warning somewhere is both another source of information in case someone just never got the memo and a prompt for someone unfamiliar with the danger, be it a kid or some ignorant adult, to potentially ask someone why that thing is dangerous. Obviously this is a bit of an extreme example since drinking unknown things is a foolish thing to do in general, but it makes more sense to just apply the labels when in doubt than spend effort making a judgement for every dangerous thing and potentially missing something. I’d bet that having warning labels on stuff actually slightly increases the amount of common sense in society.