Actually nicotine is not bad for you either, it is the 200 other chemicals present that lead to things like cancer. Now, both are psychoactive drugs with some addictive properties, so they aren't exactly vitamins.
As to labeling, I agree with Mike. It is up to the individual to educate themselves. Most people don't read warning labels to begin with. Additional cost and regulation that ends up being paid for by consumers is all it would be.