Ask HN: How much importance does your company give to documentation?

I have been working in Network Software Development industry for the last 5 years. Both the companies I have worked for lacks severely when it comes to any kind of documentation of the source code. Every engineer is supposed to just dig into the code base and figure out things on their own and encouraged to ask others.

When I spend hours wading through a very large code base, I always feel the need for better documentation. Some engineers do think about documenting properly, but the vigor dies down after a while and we end up with incomplete/outdated comments/references which does more harm than good. Is this attitude pretty common in the industry? What is your opinion on this? Are there companies that get it right?