This. And all this started around the same time - in 2006 -- when Stefan Esse, the PHP security expert "resigned".
In a blog post in 2006 (that can no longer be found) Esse was quoted as saying he quit > "because among other things they were resistant to his finding bugs in PHP, and had refused to patch some of the bugs he found."
Source(s)
http://www.darkreading.com/risk/php-security-expert-quits/d/...?
https://preilly.me/2006/11/09/php-security-expert-resigns/
PHP is the backbone of WordPress and none of the core team members have taken any of it's security holes seriously, many of which can be traced back to PHP's security hole. They simply come out with "It's the Plugin-Developer's fault" every few months when a security hole is found.
I don't think it's in their best (business) interest to fix WordPress' security holes any time soon. Because Matt Mullenweg, and other "Wordpress Security" companies like Sucuri Security, even WP Engine, all charge an arm and a length (WP Engine is 100$ a month for a simple blog serving < 25K pageviews a month) by selling "Peace of Mind" security with Wordpress if you use them / host with them.