And that's reason #1 we don't use Github. Assembla lets us host all of our git, SVN and Mercurial repos for free.. currently we have 32 and counting, no issues ever, without paying a single penny.
Granted, the prices might be steep/strange, but I see no problem in charging for things that people don't want to share on a social code sharing site.
I've learned a lot from reading other people's code and I still think it's one of the best ways to learn new languages and techniques.
I'd love to use Github and all, Github's cool. But I can't justify paying that much for private repositories. Even with all of the annoying junk on the site, Assembla's free plan won hands down.
In the case of Assembla, their business is consulting and the site is a loss leader for that division.
This quite effectively explains both the pricing and feature set differences.