What added value do academic publishers provide?

Question

As per the title; this is something I've wondered about for quite a while, but the recent news about MIT and Elsevier (and UC a while ago, although it looks like negotiations have started anew there) reminded me. It seems to be to be the case that they don't, especially now that most journals/proceedings are published solely in digital format; there would seem to be literally zero cost or skill involved in watermarking a PDF and hosting it online, heck, the arXiv does this for free, and it seems that more and more this is all academic publishers are doing. If reviewers were being paid then that might be one explanation, but they aren't.For textbooks, etc., I can see that there is some cost involved in providing proof reading services, but the cost of academic textbooks is clearly far too high if this is the only service being provided; the existence of freelance proof readers and well established print-on-demand services leaves me at a loss as to why academic publishers still exist at all. But since they do, and universities/institutions haven't banded into a cartel to run their own publishing, it would seem that there must be some reason that the publishers are still in business; it is just down to the corruption that seems to be rife at the very top ranks of academia (publishers giving kickbacks to chancellors), or is there a valid reason for this?

pen2l · Accepted Answer

The good ones are indeed pretty good filters. I'm not smart enough nor free enough to verify that a study is good, is important, is free of errors -- and so I benefit from the service provided by, say, Nature Photonics in knowing that whatever I'm reading is important, significant in some manner, and interesting.
Good journals have a high bar for writing and diagrams. In order to understand things, it helps that they're communicated clearly. You're likely not going to find incomprehensible poorly written text or hard-to-understand figures in Science or Cell journal.
As an example, I encourage you right now to go to https://science.sciencemag.org/ to see their coverage of covid-19. You'll get better cutting-edge information and perspective on the issue than anywhere else.

enchiridion · Answer

I recently saw a comment here about this. I don't remember the specifics, but basically the argument was based on trustworthy long-term hosting of obscure material.

lazyjeff · Answer

They find the volunteers, coordinate them, figure out and handle the paperwork, and politely hassle them until they do their work. Basically, a similar function to university administrators, mid-level government employees, corporate project managers, and non-profit directors.