Personal time commitments are understandable, but I feel like they are just an excuse in 90% of the cases. As 37signals puts it, "No time is no excuse". If you are serious about improving your abilities and buy into the craftmanship model at all, you can surely find a few hours of month to work on something, anything. Trade an hour of TV watching for an hour of writing your own blog engine or a Todo list app. Or write something to improve some small bit of your life (a program that emails you once a month to remind you to take your SO out for a nice dinner), put that on github. Don't make it out like you have to write the next Rails or jQuery to put code online.
The rest of your issues are largely related to workplace culture.
If you work at a company that uses any open source code (and I know there are some cases that don't due to federal validation and redtape etc etc), you have probably found a bug at some point. Put in an issue on github - send a pull request if you feel ambitious or if you had to monkeypatch the code for your project anyways. I have a feeling that people that work for closed/IP-hungry companies will go to the same kind of company when they change jobs. And that is fine, for some people software is just a job; but those are not the kind of people that read HN or software blogs anyways.
I know you are probably playing devil's advocate here, but every time someone posts about why developers should have side projects or github accounts, these points all get brought up and it bugs me.