Onto latest PHP officially but still offer older versions with CloudLinux - The good thing about CL is that they continue to issue security patches for older versions themselves so whilst it's not recommended to utilise older versions, at least they are still safe for customers to use.
Does CloudLinux also provide injection patching for old Joomla! 1.5 scripts that use these outdated versions of PHP?
Or is CloudLinux just providing these old versions of PHP so you can give your clients a false sense of security that "hey, everything's alright... keep using a decade's old CMS with this secure version of PHP 5."
Why do people need to use old and end-of-life versions of PHP? Ask yourself that question.
And the answer will be something along the lines of ... "My *insert script name and version* script doesn't work with PHP 7.1 or later" (In my example, I just happened to use Joomla! 1.5 but you can really insert any script and version that fits the bill here).
So the question then becomes... why are you using that script and that version of the script? Has the script been abandoned by it's developers? Are you refusing to update the script to the latest version?
Using my example of Joomla! 1.5 ... Joomla! has release several versions since 1.5 and 1.5 is now officially dead to Joomla! ... so why are you using and end-of-life and dead version of Joomla!?
Being able to use end-of-life versions of PHP - no matter how much they are propped up with the latest security fixes - isn't going to protect you from exploits in the outdated software you are using with those end-of-life versions of PHP.