Besides what joshmanders said, I would argue a change in license is usually caused by a change in code and would also mark historically when a project went from X to Y. A README will probably also need to change with new code changes. As for having contributions file. I'm not really for that, but not against it either.

The problem isn't that it's just one file (actually 2 if you're counting pr templates), the problem is we're just going to continually get this pollution of the project because it'll become "acceptable." Slippery slope and what not.

I mean at this point why is the wiki in it's own space and not git versioned? (Put it in github-wiki folder!) Why have separate gh-pages as well? (Just stick them in github-web folder!). Just shovel everything into one git repo. Don't forget the .githubconfig file in case you want to programmatically config a repository instead of going into it's options menu. And on, and on, and on.