This "hosting service" is an academic journal. They do not only host the document but also organize review of submitted papers, edit the document for publication, and ensure long-term archival of published works. And - most important for academic researchers - publishing in a respected journal improves your reputation. Once your paper gets published, you essentially sign away most rights to the publisher (see also the comment on Open Access in this discussion thread).

Whether these publishers contribute enough to warrant the high price of their publications is debatable.

Scientific publishing isn't just about putting stuff somewhere for people to read it. Publishers, through their parasitic relationship with academia, have kept themselves relevant through the critical mass of people continuing to use them.

The purpose served by publishers isn't really the hosting of articles, it's the names of journals the publishers own which carries an implication that top-tier journals get better reviewers and therefore higher quality articles. As long as academia values impact factor and journal rankings, the parasite can subsist.

Most academics tend to self-host preprints, or stick them on arXiv so the publisher as a hosting service isn't really the "value-add" offered.

>Most academics tend to self-host preprints, or stick them on arXiv so the publisher as a hosting service isn't really the "value-add" offered.

That is not true for chemistry or biology. Tell them what arXiv is and they will say, huh?