Because it's deployed on nearly every web server and has ubiquity. If you're building a web app and you want people to be able to run, chances are good if you build it in PHP, people can run it. Would be nice to say the same thing about server-side JS.
I think I'm lost on the joke; nobody wants to be the next overhyped (and polarizing) framework that is beloved by a large niche of programmers and launches a new segment of the industry?
Care to clue me in? (being honest; maybe I missed some news recently)