The TeX community in general has a philosophy that anything written since 1983 (TeX'83) or so should a) compile and b) produce precisely the same typeset document if it is recompiled today. This has obnoxious issues and is one of the reasons for the profusion of packages--the norm is to change the name for incompatible changes so that old users can continue on.
Which is a ridiculous goal, because, in general, most documents found in the wild are portable if transported together with the author's computer system. Chances of successfully producing typeset output from a .tex file (+ a bunch of external files) that you get from someone else are slim to none.
I'm glad there is a movement to do something. I used to use TeX but stopped a long time ago, because it was simply too much pain for too little gain. I still have to deal with it sometimes when helping my wife who publishes scientific papers. Whenever she mentions that she needs "a small modification in the BibTeX style", I get nightmares.
Actually anything that's gotten as far as journal publication should be exactly reproducible; I remember having to include the packages I was using and everything else in one archive for my couple of journal publications. Conceded that folks are not quite so careful for off the cuff work; same thing as having file:/// URIs in web pages.
And I'm hesitant to complain about it too greatly; my father's PhD thesis cannot be reproduced without a specific type ball for a Selectric and I know of numerous people who have kept dragging their old text files off disk packs to magtape to 8" disks to 5 1/4" disks to 3 1/2" disks and finally to CD ROMs where they have to duplicate all the CDs every few years lest they become unreadable due to dye fade. I know several photographers who are downright paranoid about an almost literal bitrot—if you ever want to see someone spitting mad with rage, telling a photographer that his precious negative or RAW file cannot be located, or read, or even decoded (a nontrivial issue with RAWs and older image formats, and depending on language and system even with text files!) will get you there.
Saying "if you preserved the files, we will recreate your masterpiece exactly" might be an overreaction to this but it's not impossible to understand where people are coming from. Particularly the poor dears coming from Word where moving a document from 2002 to 2008 will change the typesetting subtly and sometimes not so subtly.
People who downvoted me obviously never had to deal with documents that you have to process with TeXLive greater than something, and then only with particular fonts properly installed in the system (ever tried to install an OTF font? ever seen UTF-8 or ISO-8859-2 character encoding in a document?). Not to mention obsolete versions of packages that the author had on his system.
Well, I did have to deal with such documents, hence my comment. It was an informed rant.
