[csn]

I would guess one of the reasons to be the fact that there are a myriad of (money-free) hosting providers out there offering plain drag&drop file uploading with PHP support (often paired with a mysql database access). This makes PHP software extremely easy to install.

Not that it would be even possible to run non-PHP server side scripts with majority of said providers...

[ocdtrekkie]

Indeed. I follow the Wekan Kanban board project which is Meteor-based, and it seems like it's every couple weeks someone asks "how do I install this with cPanel" (which generally means, shared hosting with PHP/MySQL). It's kinda sad to explain to them that their existing hosting probably isn't going to let them run Meteor.