Linux was never meant to be used by a large number of unvetted users, and is therefore extremely prone to hacking. It is far too easy for a hacker to obtain an account on your server by using a stolen credit card and signing up or by abusing an outdated script one of your customers has not updated for years. After that, a hacker has inside access to the server and can begin poking around and attacking your server. That leaves you with the nightmare of cleaning up your hacked server.
CloudLinux OS prevents this nightmare from happening. With CageFS, users are virtualized to their own file systems, preventing any individual user from seeing any other users on the server.