Earlier quoted context omitted.
PLOS is a non-profit, and employs full-time professional editors. People forget the weird workflow in any journal that does biomedical work (including most of the PLOS family): manuscripts are submitted as Word files, then converted to XML and reformatted by a semi-automated process. There's manual labor involved to format the references and cross-references, mark up tables and figures, and proofread the HTML, PDF, a…
For all that matters , a badly formatted "times 12" word document is just as fine as a "polished" research article. This is science we are talking about, it's not an infomercial. Besides, all journals have strict and long guidelines that all presumbissions follow. I just don't buy the manual labor argument.
Proper formatting makes it possible to automatically extract bibliographic reference data, text-mine the contents for whatever interesting purposes you might think of, display it in apps and new formats, and store it for decades in a stable format.