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.
Your local bakery can rely on local customers who likely walk right by it. They produce inexpensive products that are relatively easy and quick to produce.
Not every business is like that. Maybe they spent a lot of money upfront on research and development and need to shift x units by a certain time to make it work financially? How could they do that if they have no physical presence on the high street and without telling people at scale that they exist?
Open source software is generally free, written by volunteers. There isn’t the financial pressure to sell and recover costs by a certain time.
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.