I'm not sure you're right. There are at least two reasons for expecting people to read long forms:
1) Sometimes you need to tell a story to get people to see a point. Merely stating the facts won't do it. You need to slowly lead them somewhere, while drawing a landscape, pointing out some of the pitfalls they would have pointed out, telling them how you avoided them. You need time to draw people into your line of thinking let something sink in
It's much like with security issues: if you report them, nothing happens. If you extract the details of a thousand customers and present those, people get upset and take action. The first approach is short and to the point, but does not achieve the goal, but the goal is inherently inachievable by short-and-to-the-point approaches.
I know I've been persuaded by stories where short factual statements didn't succeed, because I didn't take the time to turn the facts into the story for myself.
2) If short reports are good enough for the CTO, any manager between you and the CTO will think short reports are good enough for him as well. You will never get the chance to make a subtle point that requires some paragraphs, because nobody will read it.
There is a general complaints about a cultural change in this direction that the internet supposedly induced, but I believe it started much earlier, with the growth of megacorporations where people were expected to consume more information than they could possibly handle.
To cope, they started to consume summaries by supposedly smart advisors that they trusted. However, they also get to randomly disregard such summaries when they feel like it (out of intuition if we're being generous), because they can always say "well, it's actually complex" and they get to excuse themselves in the same way. Short reports often actually aren't good enough at all, but we've learned to live with it, because some wrong decisions are better than no decisions at all.
There is a way in between, where you sometimes, when the issue is important enough, do read the long form. Even top-level CEO's may be interested in an 800 page book on 'The better angels of our nature'. Yegge may be important enough, and his subject matter may be important enough, that Brin should actually read it entirely.
