Because it used to work without JS, but more importantly because it used to work better without JS – stuff loaded more quickly and the overall experience felt snappier. Not sure if it is front page worthy but it is still sad.
Probably because they also significantly regressed page load times when they decided to asynchronously load the most important part of the page (i.e. the source file or Readme you are navigating to).
Lean, mean javascript only bothers hardliners. But everybody suffers a user experience hit from async-javascript-for-the-sake-of-it