PHP is regarded as the most insecure technology on the internet, which makes it dangerous, especially as most websites are built using PHP. Web builders like WordPress, Joomla, Magento and most others are essentially applications made using PHP.
A small number of PHP functions, including exec() proc_open() and system(), are disabled on our Personal, Business and Reseller hosting servers. As these are shared hosting servers, they contain multiple cPanel accounts and clients on each server. To maintain the security of our clients, their emails and websites (almost all of which are businesses) we have to maintain a strict security policy and aren't able to enable them for any individual users or cPanel accounts.
The list of disabled functions is based on up to date security recommendations by the cPanel company. Almost all hosting companies which use cPanel will have a similar security protocol in this regard.
The functions are most commonly used by minor plugins and themes for WordPress, Joomla or alternatives. The best option, in this case, would be to look for an alternate plugin or theme which doesn't have those requirements.
If you absolutely need the use of disabled PHP functions, you will need to consider moving your website to a VPS or Blaze server. On these environments, your website has its own dedicated environment, which lessens the security risk those functions present (although a risk to your website still exists).
You can find details of our VPS and Blaze Server products here: