Two major things:<p>X11, although at least Xorg doesn&#x27;t run as root in modern distros any more. Wayland is the replacement but isn&#x27;t there yet.<p>Linus hates security people and refuses patches that improve security within the Linux kernel. <a href="http:&#x2F;&#x2F;www.washingtonpost.com&#x2F;sf&#x2F;business&#x2F;2015&#x2F;11&#x2F;05&#x2F;net-of-insecurity-the-kernel-of-the-argument&#x2F;" rel="nofollow">http:&#x2F;&#x2F;www.washingtonpost.com&#x2F;sf&#x2F;business&#x2F;2015&#x2F;11&#x2F;05&#x2F;net-of-...</a>