I blame the R documentation standards. They force a package author to produce a useless alphabetically-listed pdf, and many people just stop at that point.
Without any standards at all, people would have at least produced a readme.txt, which would have been a huge improvement -- e.g. I much prefer working with unfamiliar user-written Matlab packages :)
I don't know why so many people complain about R documentation, I think it's pretty good. The PDFs are useless for sure, but you don't have to use that. Emacs displays documentation pages in a split window. Or you can use a web browser.
I am (sort of); but most packages don't have vignettes. Zoo and ggplot2 (and a few other major packages) have great documentation, but they are an exception.
Without any standards at all, people would have at least produced a readme.txt, which would have been a huge improvement -- e.g. I much prefer working with unfamiliar user-written Matlab packages :)