The people spamming bigger dick pills, viagra, and the like back in the day made money, and in some cases quite substantial amounts of it. They did so simply for the fact that even if 99.9999% of people didn't go for it, that 0.00001% was far more than enough to show a healthy profit after 'advertising' costs.
The point is that advertising won't end until the formula of additional_ad_driven_revenue > ad_costs becomes false. And we're a long ways away from that given how inordinately expensive advertising is relative to the costs incurred by the companies selling the advertising. And each time that equilibrium price goes lower, the potential market of advertisers who may purchase ads grows.
This logic suggests that, if anything, advertising will get even worse as ad revenues decline. Go low enough and we'll be right back to square one with Google Ads promoting big dick pills and viagra. That's to say nothing of the fact that as revenues decline, both Google and advertisers will be looking for ever more insidious and forceful ways to make you watch and make you consume. Imagine, for instance, the countless dystopias things like Google Nest could enable - if such products ever managed to gain widespread adoption.
