alt Hacker NewsI think one of the problems is people thinking kids are more stupid than they are, and blanket "don't do that" statements without explanations don't really work for kids.
If they had told you they were highly poisonous instead of just telling you "not to eat them" you might have taken them more seriously. And if they had given you a taste of the red berry around it (which is sweet but not that special either, and the texture is not great) you might just have thought it was not necessary to play with them at all.
But that requires education at all levels, around here (Belgium) I sometimes see parents who seem deadly afraid of anything nature, I tell my kids to eat blackberries and they softly tell their kids next to us not to do that. You end up with generations who just don't know anything about what's around them and will eventually do stupid things.
It takes longer than people tend to think before kids learn to infer things well at all, and so being explicit about causal chains tends to make kids more likely to take advice. E.g "put your coat on" might not lead the child to think it is cold, and even a "put your coat on, it's cold outside" might still not lead the child to realise that means they'll freeze without the coat. A lot of tantrums would be avoided if parents were more explicit about why they're giving certain advice.