Advertisers have no incentive to promote better products than what the competition offers, they only have incentive to get people to buy their inferior products that provide them better margins than the competition.
> not many people would know about—let alone buy—video games
So you are saying in the absence of manipulative ads, kids would be consuming drugs rather than games. I highly doubt that. And from personal experience, my brother is a Minecraft addicted nutter because of peers pushing him towards it, not advertising. I've never seen ads for Minecraft, yet it is one of the most successful video game properties ever.
I didn't learn about video games through advertising, I learned about them because my friends played them. If you know somebody who's never played a video game then you'll naturally want to show them one. If somebody has the social connections to buy illegal drugs then they almost certainly have the social connections to learn about video games through word of mouth.
If there were no advertising, not many people would know about—let alone buy—video games. But dollar for dollar video games are much better for them than alternatives like drugs.