Again, I didn't say that what they do is the right way to do it, but what about discoverability? Would researchers just submit their document to every library in the world? If no entity is vetting these papers in a basic way, what's to prevent the entire channel from being taken over with spam? Is it done entirely by URL, and what's to stop the cited content from changing? What if they lose their domain? Is the similar domain that pops up with similar content the same author or someone that just ripped the site and is going to start serving up ads as soon as everyone switches their URIs? Or maybe we'd have libraries go out and actively retrieve this stuff rather than passively accepting it-- Would they monitor... mailing lists? What if someone posts a timely and incredibly controversial paper that lists a respected authority that just died as its author? What's to stop an author that published a bullshit paper from passively claiming it was a forgery? Would you, currently, give equal weight to citations published in the New England Journal of Medicine and a google doc with a bunch of citations to other google docs and personal websites? If we have centralized locations for this work, how would they not be publishers? Beyond that, current URL citations are a fucking mess. Link rot is a huge problem and most of the people that make citations in papers have no idea how to mitigate it.

Discoverability, relatively stable hosting, and the most base-level vetting and credibility are problems that they address, even if they do so poorly and greedily. If they went away tomorrow, so would the databases of work they manage, the APIs libraries use to query them, their mechanisms to confirm that whoever said they published something actually published it... Publishers don't have to be the answer-- I think a lot of these problems could be resolved through field organizations, librarianship and university organizations, but what's the likelihood that of universities and field organizations will try to monetize it and essentially become publishers in all of the worst ways?