Because the culture so complicitly provides it, while at the same time outlawing it: movies, music and even the LE efforts: drugs busts and drug wars. All of that is a form of advertising.

In a sense it's the perfect advertising (by both being 'free' and 'covert'), supporting the perfect industry, perfect only in the sense of a feedback mechanism ostensibly designed to stamp it out, only ends up perpetuating its profitability, by squeezing the product between its free advertising and its illegality, inflating prices and profits.

I know this is a potential flamewar topic--I'm sorry. I tried to just state what I think about it here. If you downvote/flag I'll delete it...I don't want to start another flamewar.

Half the public ads in SF are weed delivery services. (The other half are trying to sell software to start-ups.)

It might not need advertising, but there are soooooo many sales reps working to push it, so....

No marketing, but sales.

The media does enough.

D.A.R.E did a pretty good job too.

I don’t remember a pretty nice chunk of the 80s thanks to their effective advertising. Also, now I am addicted to fried eggs.