Because everyone knows the effects of cigarettes by now. Like Jesus Christ we teach the affects to school kids these days. In fact it's against advertising law not to list the ingredients on the packets and the amounts. Hell where I live the packets all must contain horrific pictures of the potential side affects.Let's see how this works with cigarettes, which are legal.
Cigarettes contain obscene amounts of nicotine to addict the first time user and I have never met a smoker who didn't say they wanted to quit. There are also very many bad ingredients. Despite taxing the cigarette company, the extra hospital visit make it a drain on the economy. They can do this because they are dicks.
Even e-cigarettes have very many bad ingredients that are not even necessary. Again, it is because they are dicks.
So how can you say you'll get rid of skunk if you legalized weed.
Skunk is not subject to consumer or advertising law, because it's illegal. No one really knows how the "seller" has tampered with the product, nor is the seller obligated to tell the customer. If it were legal then the potential side affects and higher THC would by law have to be advertised to any potential customer. If not then said customer can seek legal recourse. Thus diminishing the potential consumer base by default and holding the seller to a much higher standard of public health and safety.