BigCorp other than Google and Apple is underrepresented. Where are the guys who produce 5 billion lines of COBOL each year hanging out? Where are the SAP and IBM programmers?
Many of us also highly value work-life balance. As another commenter suggested, after 5pm I'm probably not on HN and am instead traveling, out to dinner with friends, playing sports, reading some good fiction, or whatever else is interesting this week (and before 5pm, I'm working...) Personal projects take up only some of my time. After a little while, much of the conversation here has become annoyingly tepid and it's only the rare tech-related post that I give more than a quick skim.
Edit: I will take issue with the sibling comment that for us, it's just a job that pays the bills. At least in the office I work, there is a very high professional level; we take pride in doing good work and maintaining that level, in keeping up with the state of the art, and implementing best practices. Myself and all my colleagues are all passionate about our work and it is definitely not "just a job". In my personal case, I'm fulfilled enough with my day to day work and develop as a programmer enough to take pleasure in having a varied and full personal life.
Not talking about programming outside of their workplace, in my limited experience. At least for the ones I know, programming is not a lifestyle, it's just a job that pays the bills - they care about doing it well, then leave to meet their (non-programmer) friends and talk about anything else (sports, politics, etc). As far as I know, none of them frequent community sites.
Probably running the big-ass ERP systems [0] on big-ass IBM mainframe iron on behalf of Apple and Google....their dirty little secret no-one is allowed to talk about.
:)
[0]: https://en.wikipedia.org/wiki/Enterprise_resource_planning