A huge value in having authors upload the original source, is it divorces the content from the presentation (mostly). That the original sources were available was sufficient for a large majority of the corpus to be automatically rendered into HTML for easier reading on many devices: https://info.arxiv.org/about/accessible_HTML.html. I don't think it would have been as simple if they had to convert PDFs.
How did we get here from the post about uv?