When the Internet digitizes what used to be analog assets, we often find out that jobs that were once done together end up in radically different places. The classic example are newspapers: they carried both editorial and advertisements, but it turns out that was simply a function of who owned printing presses and delivery trucks; once the Internet came along advertisers, which cared about reaching customers, not supporting journalists, switched to Facebook and Google, which had aggregated the former and commoditized the latter.
So it is with shelves: when the supply was constrained by physical space, they were extremely valuable for not just discovery but also distribution, but once the Internet made shelf space effectively infinite, it shouldn’t be a surprise that the solutions to discovery and distribution developed differently.