The idea feels like sci-fi because you’re so used to it, imagining ads gone feels like asking to outlaw gravity. But humanity had been free of current forms of advertising for 99.9% of its existence. Word-of-mouth and community networks worked just fine. First-party websites and online communities would now improve on that.
The traditional argument pro-advertising—that it provides consumers with necessary information—hasn’t been valid for decades.
Perhaps there is a difference in listing a service in some sort of index, like the phone book, versus techniques intended to develop a need (or want) where there wasn’t one otherwise, like an iPod commercial.