Last time I launched a node app, it took me a full day of messing about in AWS. Last time I launched a PHP app, it took me less than a half hour at Siteground.
You just lost a nontrivial percentage of PHP developers. Far and away the most compelling feature of PHP for a lot of their target audience is that the deploy model is "unzip this file in that folder". If I want to host my own web site but I don't want to "learn to program" there is no alternative.
it's more like "copy these files via ftp to this host" (p.s. that also includes your config.php with plain text passwords of course)
I got fed up with this a few years ago and started building http://bitmash.io (yes, shameless plug) which does some fancy filesystem manipulation to swap out the application's files during upgrades while otherwise looking like a perfectly ordinary PHP hosting provider. While I'm proud of this solution it still seems rather silly to have to jump through these sorts of hoops to handle deploys.
Tell me about it! It took me an entire day to figure out how to configure a WordPress install in order to allow it to self-update (without ftp). To do it by only granting owner and/or group write permissions, you have to figure out that you need to modify wp-config.php to define the "FS_METHOD" constant with the value "direct". Without this, WordPress code tries to be super clever with its umask settings, which only makes things worse.
It quite literally took an entire day to set up WordPress to self update. It's easy if you chmod 0777 nuke the entire install, but extremely complicated to set up with acceptable filesystem permissions. WordPress is designed to be sloppily dropped in a webroot, not to be installed by intermediate users who care about security. Well, as "secure" as WordPress can be. And to be honest, the most secure WordPress installation would be incapable of self-updating, as you're granting the web user write access to the entire installation - not just for updates, but for any vulnerability.
You can then disable wp cron, which saves network resources.
The performance characteristics of Node are completely irrelevant for most sites. The developments model's inherent complexity and the moving target, however, matters very much.
The vast majority of blogs that are build in Wordpress. Remove all the blogs and corporate websites and I bet that's not the case anymore.
And no, there's some pretty big, modern sites like Mailchimp which run on PHP.
There's literally no reason to use Node if you already have an effective backend with PHP because Node doesn't really bring anything new on the table, but it does bring along its own class of issues.
You can't write a production grade web socket server in PHP. and no ReactPHP isn't my definition of production grade. If your app is real time you just can't use PHP for that.
So yes, Node brings something new to the table.
You just said, Node brought nothing new to the table, obviously you were wrong.
I do concede that if PHP went away, WP would somehow survive, like some kind of post-nuclear cockroach.