I believe the reason can be seen on:
http://www.openbsd.org/papers/bsdcan14-libressl/mgp00025.htm...
"This page scientifically designed to annoy web hipsters"
> and not make it take an age to open in a browser
The whole page is ~484kb, which in this day is not much at all (many pages serve more css than that). I do like to complain about big pages as well, but I can't say this is one of those.
But I agree, a pdf would be sweet. My biggest complain with the site is that it doesn't work great on a mobile device (very small links, can't press on a slide to go to the next, and Firefox mobile open the page in "full size" mode with only half a slide visible without zooming back).
Why not send it to a PDF printer and cutdown that filesize (and not make it take an age to open in a browser)?