Right.... because the heaps of information that gets dumped on you whenever you receive a prescription drug or go in to surgery is oh so helpful.
You are basically advocating for an expansion of this. If a vaporize contains 100 different chemicals, and all of them come along with pages of information, the user won't be able to grok it all and realize that one of them is probably going to seriously screw them in a few years.
I don't know what you expect an informed consumer to look like, but having a person reading a booklet of medical jargon to determine health risks for each drug they take is extremely unrealistic.
So, the government is right here. We need to ban certain chemicals because there is no other way. Life is too complicated as it is.