Why the hate for PDFs, I can see why you would not want to communicate dynamic content with them, sure. But for academic papers, which are usually static text and equations and maybe some plots, PDFs do exactly what you want: At least in principle they look the same on every system.
If I want to email them to somebody, store a copy, read them offline on a reader etc. I have to deal with one single file, in a format that just works on many readers. What am I gonna do when I typeset a paper with webtechnology ... fire up a local server to display some inline math in my html page .. no thank you.
I agree that maybe layouting based on physical paper is maybe not ultimately necessary, but it gives the reader a familiar structure. The way the advertised web site is transferring the papers into a long scrolling list of text ... I find it rather disorienting and unstructured. Text that is split up into "pages" (whatever size they are in the end) somehow helps break up the reading flow.
In the end it remains to be shown that the gain from having academic papers not typeset in PDF outweighs the hassle of having to deal with non-standardized ways of rendering properly formatted text on websites (thinks like MathJax etc. do not support everything that is available in full LaTeX etc.).
But anyway, in the context of the discussion about this webpage/project, it's not relevant to ask why these PDFs exist. They do, and the scientific community is nowhere near a transition away from them. So bfirsh is trying to find a solution to consume those existing PDFs.
So think as not getting downvoted for expressing your opinion, but more for not contributing to the discussion about this particular project.
HTML is better read, smaller, faster, has more formatting options, and can have all contained in a single file.
Seriously, stop creating PDFs.