[munaf]

1. I don't need private repos yet, so GitHub is free for me.

2. If I do need private repos, I can afford GitHub.

3. GitHub has better UX and design, and its design sense has been contagious to its users. I think part of the reason people make their code/docs super-presentable on GitHub is to fit in with the look and feel of the site, but that's pure speculation and could be wrong.

4. My main use case is code discovery, not project hosting. GitHub got there first in building a community, so there's more to discover - in addition to it usually being easier to look at as per (3).