My experience is that it's too complicated for people. My parents can just about understand don't take more than 8 paracetamol/tylenol per day, or don't take advil if you've got high blood pressure, but any more complex than that and they just can't really understand it.
They can't (or don't want to) understand that certain antibiotics mix poorly with alcohol (Don't drink on antibioitics) or that some painkillers are _not_ suitable for hangovers (headache == tylenol). They don't understand how statistics of side effects work (10% of people have one or more of the following side effects means "It won't happen to me"), or that some supplements can interfere with medication (warfarin and St Johns wort), and that this is bad, even though they're not medicines.
There surely are more examples where the docs seem to be a lot less careful about giving out these drugs. Also I think, and that's not only regarding the US, but all of the world, people should be getting way more education about what these drugs are, what they cause, how they should be taken and how you should stop taking them / what risks it bears if you don't.